STATE COMMITTEE OF THE RUSSIAN FEDERATION
ENVIRONMENTAL PROTECTION
QUANTITATIVE CHEMICAL ANALYSIS OF WATER
MEASUREMENT TECHNIQUE
FORMALDEHYDE MASS CONCENTRATION
IN SAMPLES OF NATURAL AND TREATED WASTEWATER
PHOTOMETRIC METHOD WITH ACETYLACETONE
If a mass concentration formaldehyde in the analyzed sample exceeds the upper limit, it is allowed to dilute the sample in such a way that the concentration of formaldehyde corresponds to the regulated range.
Interfering influences from other sample components are eliminated by steam stripping of formaldehyde.
2. PRINCIPLE OF THE METHOD
The photometric method for determining the mass concentration of formaldehyde is based on the formation in the presence of ammonium ions colored in yellow reaction product of formaldehyde with acetylacetone. The color intensity of the resulting compound is proportional to the formaldehyde content in the sample. Measurement optical density carried out at a wavelength? = 412 nm.
3. ASSIGNED CHARACTERISTICS OF THE MEASUREMENT ERROR AND ITS COMPONENTS
This method provides the results of the analysis with an error not exceeding the values given in Table 1.
Table 1
Measurement range, values of indicators of accuracy, correctness, repeatability, reproducibility
The values of the accuracy index of the methodology are used for:
Registration of the results of the analysis issued by the laboratory;
Evaluation of the activities of laboratories for the quality of testing;
Evaluation of the possibility of using the results of the analysis in the implementation of the methodology in a particular laboratory.
4. MEASURING INSTRUMENTS, AUXILIARY DEVICES, REAGENTS AND MATERIALS
4.1. Measuring instruments
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A spectrophotometer or photometer that measures |
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Cuvettes with an absorbing layer thickness of 50 mm |
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GOST 24104-2001 |
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General purpose laboratory scales with the largest |
GOST 24104-2001 |
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СС with certified formaldehyde content with an error |
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Volumetric flasks, bulk |
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Graduated pipettes |
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Pipettes with one mark |
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Graduated cylinders |
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4.2. Auxiliary devices
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Electric tiles with closed spiral |
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Cabinet drying laboratory with |
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bath water |
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Refrigerator household |
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Cups for weighing (boxes) |
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Chemical glasses |
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V-1-1000 THS |
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Funnels laboratory |
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Formaldehyde strippers (round-bottom flasks) |
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Flasks conical |
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Kn-2-100-18 THS |
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Kn-1-250-18-29/32 KhS |
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Dropper 1(2)-50 XC |
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Glass rods 25 - 30 cm long and? 3 - 4 mm |
Measuring instruments must be verified within the established time limits.
It is allowed to use other, including imported, measuring instruments and auxiliary devices with characteristics no worse than those given in p.p. 4.1 and 4.2.
4.3. Reagents and materials
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Formaldehyde, 40% aqueous solution |
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Acetylacetone, freshly distilled |
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Ammonia water, concentrated |
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ammonium acetate |
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Sulfuric acid |
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Hydrochloric acid |
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Acetic acid |
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Potassium hydroxide or |
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sodium hydroxide |
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Potassium bichromate (potassium dichromate) or |
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potassium dichromate, standard titer 0.1 mol/dm 3 equivalents |
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Sodium thiosulfate (sodium sulphate), pentahydrate, or |
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sodium sulphate (thiosulfate), standard titer 0.1 mol/dm 3 equivalents |
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potassium iodide |
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Iodine crystalline or |
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iodine, standard titer 0.01 mol/dm 3 equivalents |
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Sodium sulfate anhydrous Na 2 SO 4 |
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Sodium carbonate anhydrous Na 2 CO 3 |
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Chloroform |
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Starch soluble |
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Universal indicator paper |
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Anesthetized filters "white tape" |
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Distilled water |
All reagents used for analysis must be of analytical grade. or h.h.
It is allowed to use reagents manufactured according to other regulatory and technical documentation, including imported ones, with a qualification of at least analytical grade.
6. OPERATOR QUALIFICATION REQUIREMENTS
Measurements can be performed by an analytical chemist who is proficient in the technique of photometric analysis and who has studied the instruction manual for the spectrophotometer or photometer.
7. MEASUREMENT CONDITIONS
When performing measurements in the laboratory, the following conditions must be met:
ambient air temperature (22 ± 6) °С;
· Atmosphere pressure(84 - 106) kPa;
· relative humidity no more than 80% at a temperature of 25 °С;
frequency of alternating current (50 ± 1) Hz;
mains voltage (220 ± 22) V.
8. SAMPLING AND STORAGE
8.1. Sampling is carried out in accordance with the requirements of GOST R 51592-2000 “Water. General requirements to sampling."
8.2. The glassware intended for sampling and storage of samples is washed with a saturated solution of soda ash (sodium carbonate), and then with distilled water. When washing heavily soiled dishes, it is recommended to use a chromium mixture, then thoroughly (at least 10 times) rinse with tap water and rinse with distilled water.
8.3. Water samples are taken in glass bottles with tightly screw caps with liners that ensure tightness, with a capacity of 0.5 dm 3 .
The volume of the sample taken must be at least 0.5 dm3.
8.4. Samples are analyzed no later than 6 hours after sampling when stored at a temperature above 10 °C without a preservative, or within 10 days when preserved with sulfuric acid at the rate of 5 cm 3 of an acid solution (1: 1) per 1 dm 3 of water.
8.5. When sampling, an accompanying document is drawn up in the approved form, which indicates:
Purpose of analysis, suspected contaminants,
Place, time of selection,
Sample number
Position, name of the person taking the sample, date.
9. PREPARATION FOR MEASUREMENTS
9.1. Preparation of solutions and reagents
9.1.1. Distilled water, purified from formaldehyde.
Distilled water is boiled for 30 minutes and cooled to room temperature. Use on the day of preparation.
9.1.2. Sulfuric acid solution, 1:1.
To 100 cm 3 of distilled water placed in a heat-resistant beaker, 100 cm 3 of concentrated sulfuric acid are added with continuous stirring and cooled. The solution is stable when stored in a tightly closed bottle for 1 year.
9.1.3. Solution of hydrochloric acid, 2:1.
To 170 cm 3 of distilled water, add 340 cm 3 of concentrated hydrochloric acid and mix. The solution is stable when stored in a tightly closed container for 6 months.
9.1.4. A solution of potassium or sodium hydroxide, 2 mol / dm 3.
56 g of KOH or 40 g of NaOH are dissolved in 500 cm 3 of distilled water. The solution is stable when stored in a tightly closed polyethylene container for 3 months.
9.1.5. Starch solution, 0.5%.
0.5 g of starch is shaken with 15 - 20 cm 3 of distilled water. The suspension is gradually poured into 80 - 85 cm 3 of boiling distilled water and boiled for another 2 - 3 minutes. After cooling, preserve by adding 2 - 3 drops of chloroform. Store no more than 1 month.
9.1.6. Standard solution of potassium dichromate with a concentration of 0 .0200 mol/dm 3 equivalents.
When using a standard titer, the latter is dissolved in distilled water in a volumetric flask with a capacity of 500 cm 3, then 50 cm 3 of the resulting solution is taken, transferred to a volumetric flask with a capacity of 500 cm 3 and the volume is adjusted to the mark with distilled water.
To prepare a standard solution from a sample of 0.4904 g of K 2 Cr 2 O 7, previously dried in an oven at 105 ° C for 1 - 2 h, transfer quantitatively into a volumetric flask with a capacity of 500 cm 3 , dissolve in distilled water and bring the volume of the solution to the mark on the flask. Store in a bottle with a well ground cork in a dark place for no more than 6 months.
9.1.7. Standard solution of sodium thiosulfate with a concentration of 0.02 0 mol/dm 3 equivalents.
When using a standard titer, the latter is dissolved in distilled water, previously boiled for 1.5 hours and cooled to room temperature, in a volumetric flask with a capacity of 500 cm 3, then 50 cm 3 of the resulting solution is taken, transferred to a volumetric flask with a capacity of 500 cm 3 and bring the volume of boiled distilled water to the mark.
To prepare a standard solution from a sample of 5 g of Na 2 S 2 O 3 ? 5H 2 O, dissolved in 1 dm 3 of distilled water, pre-boiled for 1.5 h and cooled, and bring the volume of the solution to the mark on the flask. As a preservative, 2 cm 3 of chloroform is added to the resulting solution.
Before determining the exact concentration, the solution is kept for at least 5 days. Store in a dark glass bottle for no more than 4 months.
The exact concentration of the sodium thiosulfate standard solution is determined as described in Appendix A at least once a month.
9.1.8. Iodine solution, 0.02 mol/dm3 equivalent.
When using a standard titer, the latter is dissolved in distilled water in a volumetric flask with a capacity of 500 cm 3 .
When preparing a solution from a sample of 4 - 5 g of KI, dissolve in a small amount (20 - 25 cm 3) of distilled water, add 1.3 g of crystalline iodine; after its dissolution, another 480 cm 3 of distilled water are added and mixed.
The solution is stored in a dark glass bottle.
The exact concentration of the iodine solution is set at least once a month, as described in Appendix A.
9.1.9. Acetic acid solution, 1:4.
Mix 1 volume of acetic acid with 4 volumes of formaldehyde-free distilled water. The solution is stable when stored in a tightly closed container for 3 months.
9.1.10. Acetylacetone solution, 5%.
To 38 cm 3 of distilled water add 2 cm 3 of acetylacetone and stir until complete dissolution. Store in the refrigerator in a bottle with a ground stopper for no more than 10 days.
9.1.11. Ammonium acetate buffer solution.
To 80 cm 3 of glacial acetic acid, add 90 cm 3 of concentrated ammonia solution and mix. The pH value of the resulting buffer solution should be 5.9 - 6.5. Store in a tightly closed bottle for no more than 3 months.
9.2. Preparation of calibration solutions
Calibration solutions certified according to the preparation procedure are prepared from a standard sample (RS) or a 40% formaldehyde (formalin) solution.
When using CO, the initial solution is diluted in accordance with the instructions for its use.
The preparation of a calibration solution from formalin is carried out in accordance with paragraphs 9.2.1 - 9.2.3.
9.2.1. Formaldehyde solution (A).
In a volumetric flask with a capacity of 100 cm 3, 2.5 cm 3 of a solution of potassium or sodium hydroxide, 2.5 cm 3 of distilled water and 1 cm 3 of a 40% formaldehyde solution are successively poured with a pipette. The volume of the solution was made up to the mark with distilled water and mixed. To determine the exact concentration of formaldehyde, 1 cm 3 of the resulting solution is taken into a conical flask with a ground stopper with a capacity of 250 cm 3, 20 cm iodine solution and 10 cm 3 potassium or sodium hydroxide solution are added with a pipette. The flask is stoppered and left to stand for 15 minutes in a dark place. Then add 5 cm 3 hydrochloric acid solution, mix and leave for another 10 minutes in a dark place.
The released excess of iodine is titrated with a solution of sodium thiosulfate to a pale yellow color, 1 cm 3 of a starch solution is added and titration is continued until the solution becomes colorless.
The determination is repeated 1-2 more times, and if there is no discrepancy in the volumes of the sodium thiosulfate solution of more than 0.05 cm 3, the average value is taken as the result.
The mass concentration of formaldehyde in the main solution (A) is calculated by the formula:
where C f - mass concentration of formaldehyde solution, mg/dm 3 ;
C and - the concentration of the iodine solution, mol / dm 3 equivalent;
V and - the volume of the added iodine solution, cm 3;
C t - concentration of sodium thiosulfate solution, mol/DM 3 equivalent;
V t - the volume of sodium thiosulfate solution used for titration of excess iodine solution, cm 3;
V f is the volume of formaldehyde solution taken for titration, cm 3 .
The basic solution of formaldehyde is stored in the refrigerator for no more than 1 month. Its exact concentration is established before use for the preparation of intermediate and working solutions.
9.2.2. Solution with mass concentration of formaldehyde 0.100 mg/cm 3 (B).
The volume of solution A, which must be taken to obtain 100 cm 3 of solution B with a concentration of 0.100 mg / dm 3, is calculated by the formula:
where V f is the volume of solution A, cm 3;
C f - mass concentration of formaldehyde in solution A, mg/cm 3 .
The calculated volume of solution A is placed into a volumetric flask with a capacity of 100 cm 3 using a graduated pipette, brought to the mark with distilled water and mixed. The solution is stored for no more than a day.
9.2.3. Solution with a mass concentration of formaldehyde 5 mcg / cm 3 (B).
5.0 cm 3 of formaldehyde solution B is transferred into a volumetric flask with a capacity of 100 cm 3, brought to the mark with distilled water (clause 9.1.1) and mixed. The solution is used on the day of preparation.
9.3. Construction of a calibration graph
To build a calibration graph, it is necessary to prepare samples for calibration containing 0 - 0.10 μg of formaldehyde in 25 cm 3 of solution.
The conditions for the analysis must comply with clause 7.
The composition and number of samples for constructing a calibration curve are shown in Table 2.
For all calibration solutions, the errors due to the preparation procedure do not exceed 3% relative to the assigned value of the mass concentration of formaldehyde.
When constructing a calibration graph, 20 cm 3 of distilled water are added to volumetric flasks with a capacity of 25 cm 3 (clause 9.1.1), aliquots of formaldehyde solution B are added with graduated pipettes with a capacity of 1 or 2 cm 3 in accordance with table. 2, bring the volumes of solutions in flasks to the mark, mix and transfer into conical flasks with a capacity of 100 cm 3 .
table 2
Composition and number of samples for calibration in the determination of formaldehyde
The analysis of samples for calibration is carried out in ascending order of their concentration according to clause 10, excluding the stage of distillation.
Measure the optical density of samples with formaldehyde additives and a blank (containing no additives) samples at? = 412 nm, photometrically 3 times to eliminate random results and average data. Subtract the average optical density of the blank sample from the average optical density of the samples with formaldehyde additives.
The calibration graph is built in coordinates: the content of formaldehyde in the sample for calibration, μg - optical density.
9.4. Controlling the stability of the calibration characteristic
The stability control of the calibration characteristics is carried out at least once a month or when changing the main reagents (acetylacetone, ammonium acetate, buffer solution). The means of control are newly prepared samples for calibration (at least 3 samples from those given in Table 2).
The calibration characteristic is considered stable if the following condition is met for each sample for calibration:
|X- C| ? 1,96?Rl,
where X- result control measurement mass concentration of formaldehyde in the calibration sample;
With- certified value of the mass concentration of formaldehyde in the sample for calibration;
?Rl- standard deviation of intralaboratory precision, established during the implementation of the methodology in the laboratory.
Note . It is permissible to establish the standard deviation of the intralaboratory precision when implementing the methodology in the laboratory based on the expression: ? Rl = 0,84?R, with subsequent refinement as information accumulates in the process of monitoring the stability of the analysis results.
Values? R are shown in table 1.
If the stability condition for the calibration characteristic is not met for only one calibration sample, it is necessary to re-measure this sample in order to eliminate the result containing a gross error.
If the calibration characteristic is unstable, find out the reasons for its instability and repeat the stability control using other calibration samples provided by the procedure. When the instability of the calibration characteristic is detected again, a new calibration curve is built.
10. MEASUREMENTS
A sample of water with a volume of 200 cm 3 is placed in a distillation flask (if conservation was performed, the sample is first neutralized with a solution of KOH or NaOH to pH 7 - 8 according to universal indicator paper), 25 g of sodium sulfate is added, the parts of the installation for stripping formaldehyde are connected and distilled into a measuring cylinder 100 cm 3 distillate.
The distillate is thoroughly mixed with a glass rod, taken with a 25 cm 3 pipette, placed in a 100 cm 3 conical flask, 2 cm 3 of an acetate-ammonium buffer solution (or 2.0 g of ammonium acetate and 0.5 cm 3 of a 1:4 acetic acid solution) are added ) and 1.0 cm 3 of acetylacetone solution. The mixture is stirred until complete dissolution of the reagents and kept in a water bath for 30 min at (40 ± 3) °C. Simultaneously with the sample, a blank determination is made using 25 cm 3 of formaldehyde-free distilled water.
Measure the optical density of the solutions relative to distilled water at 412 nm in cuvettes with an absorbing layer thickness of 5 cm. The optical density of a blank experiment is subtracted from the optical density of the sample.
If the measured optical density of the sample exceeds the optical density corresponding to the last point of the calibration curve, repeat the determination with a smaller aliquot of distillate diluted to a volume of 25 cm 3 with distilled water that does not contain formaldehyde (section 9.1.1).
11. PROCESSING OF MEASUREMENT RESULTS
Mass concentration of formaldehyde in the analyzed water X, mg / dm 3, calculated by the formula:
100 - distillation volume, cm 3 ;
1.2 - coefficient taking into account the degree of formaldehyde distillation from water samples;
V d - the volume of the distillate aliquot, cm 3 ;
V in - the volume of the water sample taken for distillation, cm 3.
The discrepancy between the results of the analysis obtained in the two laboratories should not exceed the limit of reproducibility. If this condition is met, both results of the analysis are acceptable, and their average can be used as the final one. arithmetic value.
The value of the reproducibility limit R at Р = 0.95 for the entire regulated range of measurements of the mass concentration of formaldehyde is 22%.
If the reproducibility limit is exceeded, methods for checking the acceptability of the results of the analysis according to section 5 of GOST R ISO 5725-6 can be used.
12. PRESENTING THE RESULTS OF THE ANALYSIS
Analysis result X in documents providing for its use, it can be represented as:
X ±?, mg / dm 3, P \u003d 0.95,
where? - an indicator of the accuracy of the method.
Meaning? calculated by the formula:
0.01? d? X.
The value of d is given in table 1.
It is permissible to present the result of the analysis in the documents issued by the laboratory in the form:
X ± ? l, mg / dm 3, P \u003d 0.95,
given that? l < ?,
where X- the result of the analysis obtained in accordance with the prescription of the methodology;
±? l- the value of the characteristic of the error of the results of the analysis, established during the implementation of the methodology in the laboratory, and provided by the control of the stability of the results of the analysis.
The numerical values of the measurement result must end with a digit of the same digit as the values of the error characteristic.
13. QUALITY CONTROL OF THE RESULTS OF THE ANALYSIS DURING THE IMPLEMENTATION OF THE METHOD IN THE LABORATORY
Quality control of the analysis results when implementing the methodology in the laboratory provides for:
Operational control of the analysis procedure (based on the assessment of the error in the implementation of a single control procedure);
Control of the stability of the results of the analysis (based on the control of the stability of the standard deviation of repeatability, standard deviation of intralaboratory precision, error).
13.1. Algorithm for operational control of the analysis procedure using the additive method
K to with control standard TO.
Toto calculated by the formula:
K k \u003d | X "- X - C d |,
where X" - the result of the analysis of the mass concentration of formaldehyde in a sample with a known additive;
X- the result of the analysis of the mass concentration of formaldehyde in the original sample;
C d- the amount of the additive.
Control standard To calculated by the formula:
where? l,X", ?l, X- values of the error characteristic of the results of the analysis, established in the laboratory when implementing the methodology, corresponding to the mass concentration of formaldehyde in the sample with a known additive and in the original sample, respectively.
Note . l= 0.84? ?, with subsequent refinement as information accumulates in the process of monitoring the stability of the analysis results.
K to ? TO. (1)
If condition (1) is not met, the control procedure is repeated. In case of repeated non-fulfillment of condition (1), the reasons leading to unsatisfactory results are found out and measures are taken to eliminate them.
13.2. Algorithm for operational control of the analysis procedure using control samples
Operational control of the analysis procedure is carried out by comparing the result of a single control procedure K to with control standard TO.
The result of the control procedure Toto calculated by the formula:
K to = |X k - WITH|,
where X k- the result of the analysis of the mass concentration of formaldehyde in the control sample;
With- certified value of the control sample.
Control standard To calculated according to the formula
K = ?l,
where ±? l- characteristic of the error of the results of the analysis, corresponding to the certified value of the sample for control.
Note . It is permissible to establish the error characteristic of the analysis results when implementing the methodology in the laboratory on the basis of the expression: ? l= 0.84? ? with subsequent refinement as information accumulates in the process of monitoring the stability of the analysis results.
The analysis procedure is considered satisfactory if the following condition is met:
K to ? To. (2)
If condition (2) is not met, the control procedure is repeated. If condition (2) is not met again, the reasons leading to unsatisfactory results are found out and measures are taken to eliminate them.
The frequency of operational control of the analysis procedure, as well as the ongoing procedures for monitoring the stability of the analysis results, are regulated in the Laboratory Quality Manual.
Annex A
(mandatory)
Establishment of the exact concentration of standard solutions of sodium thiosulfate and iodine
A.1. Sodium thiosulfate solution
80 - 90 cm 3 of distilled water, 10.0 cm 3 of a standard potassium bichromate solution are added to the titration flask, 1 g of dry KI and 10 cm 3 of hydrochloric acid solution are added. The solution is stirred, kept for 5 minutes in a dark place, and the sample is titrated with a solution of sodium thiosulfate until a slightly yellow color appears. Then add 1 cm 3 starch solution and continue dropwise titration until the blue color disappears. The titration is repeated and, if the discrepancy between the values of the titrant volumes does not exceed 0.05 cm 3, their average value is taken as the result. Otherwise, repeat the titration until results differ by no more than 0.05 cm 3 .
The exact concentration of sodium thiosulfate solution is found by the formula:
where C t is the concentration of a solution of sodium thiosulfate, mol / dm 3 equivalent;
C d - concentration of potassium bichromate solution, mol/dm equivalent;
V t is the volume of sodium thiosulfate solution used for titration, cm 3;
V d - the volume of potassium bichromate solution taken for titration, cm 3.
A.2. Iodine solution
60 - 70 cm 3 of distilled water are added to the titration flask, 20 cm 3 of iodine solution, 10 cm 3 of hydrochloric acid solution are added with a pipette and titrated with sodium thiosulfate until a pale yellow color. Then add 1 cm 3 of starch solution and titrate dropwise until the solution becomes colorless. The titration is repeated 1 - 2 more times, and in the absence of discrepancies in the volumes of sodium thiosulfate solution of more than 0.05 cm 3, the average value is taken as the result.
Foreword
The goals and principles of standardization in the Russian Federation are established by the Federal Law of December 27, 2002 No. 184-FZ "On Technical Regulation", and the rules for the application of national standards of the Russian Federation - GOST R 1.0 - 2004 "Standardization in the Russian Federation. Basic Provisions” Information about the standard 1. PREPARED by the Open Joint Stock Company “Research Center for Control and Diagnostics of Technical Systems” (OJSC “NITs KD”) based on its own authentic translation of the standard specified in paragraph 4 2. INTRODUCED by the Technical Committee for Standardization TK 457 “Air quality” 3. APPROVED AND INTRODUCED BY Order of the Federal Agency for Technical Regulation and Metrology dated December 27, 2007 No. 590-st 4. This standard is identical to the international standard ISO 16000-3:2001 “Indoor air. Part 3. Determination of the content of formaldehyde and other carbonyl compounds. Active sampling method" (ISO 16000-3:2001 "Indoorair - Part 3: Determination of formaldehyde and other carbonyl compounds - Active sampling method"). When applying this International Standard, it is recommended that the corresponding national standards be used in place of the referenced International Standards, details of which are given in additional applicationС 5. INTRODUCED FOR THE FIRST TIME Information about changes to this standard is published in the annually published information index "National Standards", and the text of changes and amendments - in the monthly published information indexes "National Standards". In case of revision (replacement) or cancellation of this standard, a corresponding notice will be published in the monthly published information index "National Standards". Relevant information, notification and texts are also posted in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet
| 1. Scope 2. Normative references 3. Summary of the method 4. Limitations and interfering substances 4.1. General provisions 4.2. Interfering effect of ozone 5. Safety requirements 6. Equipment 7. Reagents 8. Preparation of reagents and cartridges 8.1. Purification of 2,4-dinitrophenylhydrazine 8.2. Preparation of DNPH derivative of formaldehyde 8.3. Preparation of initial solutions of DNPH derivative of formaldehyde 8.4. Preparation of cartridges with DNPH deposited on silica gel 9. Method 9.1. Sampling 9.2. Blank samples 9.3. Sample analysis 10. Calculation of measurement results 11. Performance criteria and quality control of measurement results 11.1. General provisions 11.2. Standard Operating Procedures 11.3. HPLC System Efficiency 11.4. Loss of sample 12. Precision and uncertainty Appendix A (informative) Precision and uncertainty Appendix B (informative) Melting points of DNPH derivatives of carbonyl compounds Appendix C (informative) Information on the compliance of the national standards of the Russian Federation with reference international standards Bibliography |
Introduction
This part of ISO 16000-2 applies to the analysis of indoor air during sampling. The standard is used in the determination of the content of formaldehyde and other carbonyl compounds. The standard has been tested against 14 aldehydes and ketones. Formaldehyde is the simplest carbonyl compound, consisting of one carbon atom, one oxygen atom, and two hydrogen atoms. In its pure form in the monomolecular state, it is a colorless, pungent, reactive gas. Formaldehyde is used in the production of urea-formaldehyde polymers, adhesives and insulating foams. The main source of formaldehyde in indoor air is its release from particle boards and insulating materials used in construction. Sampling for formaldehyde content is carried out by pumping air through a reactive medium, which results in a derivative compound with a lower vapor pressure, which is more effectively retained in the sampling device and can be more easily analyzed. This International Standard specifies a method for the determination of formaldehyde and other carbonyl compounds, which is based on the reaction of these compounds with 2,4-dinitrophenyl-hydrazine supported on a sorbent to convert them to the corresponding hydrazones, which can be recovered and measured with high sensitivity, precision and accuracy. The procedure given in this International Standard is also applicable to the determination of other carbonyl compounds released into the air by solvents, binders, cosmetics and other sources. The sampling methodology given in this standard is based on the TO-11 A method [1]. When applying the methodology specified in this standard, it should be taken into account that formaldehyde and some other carbonyl compounds are highly toxic substances [2].
NATIONAL STANDARD OF THE RUSSIAN FEDERATION
Introduction date - 2008-10-01
1 area of use
This International Standard specifies a method for the determination of formaldehyde (HCHO) and other carbonyl compounds 1) (aldehydes and ketones) in air. The method used for the determination of formaldehyde, after appropriate modification, is used for the detection and quantification of other carbonyl compounds (at least 13 compounds). The method is used to determine formaldehyde and other carbonyl compounds in the mass concentration range from approximately 1 µg/m 3 to 1 mg/m 3 . Using the method given in the standard, a time-averaged sample is obtained. The method can be used for both long-term (from 1 to 24 h) and short-term (from 5 to 60 min) air sampling to determine the formaldehyde content in it. This International Standard specifies a procedure for the collection and analysis of air samples to determine the content of formaldehyde and other carbonyl compounds in air by capturing them from the air using 2,4-dinitrophenylhydrazine (DNPH) coated cartridges and then analyzing by high performance liquid chromatography (HPLC) with ultraviolet ( UV) detector [1], [3]. The method given in the standard was developed specifically for the collection and analysis of samples for the determination of formaldehyde in air using a cartridge filled with an adsorbent and subsequent HPLC. The method is also applicable to the determination of other aldehydes and ketones in the air. 1) In this standard, the common names of compounds are given instead of the names according to the PAC ID nomenclature given in brackets: formaldehyde (methanal); acetaldehyde (ethanal); acetone (propane-2-he); butyric aldehyde (butanal); crotonaldehyde (2-butenal); isovaleric aldehyde (3-methylbutanal); propionaldehyde (propanal); m - toluylaldehyde (3-methylbenzaldehyde); o - toluylaldehyde (2-methylbenzaldehyde); p - toluylaldehyde (4-methylbenzaldehyde); valeraldehyde pentanal. The method given in this International Standard is applicable to the determination of the following carbonyl compounds:2. Regulatory references
This standard uses Normative references to the following standards: ISO 9001:2000 Quality management systems. ISO 16000-1 requirements Indoor air. Part 1. Sampling. General provisions ISO 16000-2 Indoor air. Part 2: Formaldehyde sampling methodology ISO 16000-4 Indoor air. Part 4. Determination of formaldehyde. Diffusion sampling method ISO 17025:2005 General requirements for the competence of testing and calibration laboratories3. The essence of the method
This International Standard specifies a method for pumping air through a cartridge containing silica gel coated with DNPH. The method is based on the specific reaction of the carbonyl group of the analyzed compound with DNPH in the presence of an acid to form stable derivatives (Figure 1). The starting aldehydes and ketones are determined from their DNPH derivatives by HPLC using a UV or diode array detector. Other carbonyl compounds may be determined by the indicated detection methods according to 9.3.5. This International Standard provides guidance on the preparation of sampling cartridges based on commercial chromatography cartridges containing silica gel by introducing acidified DNPH into each cartridge. It is recommended to use commercially available cartridges containing DNPH-coated silica gel, as they are more uniform and have low blank readings. However, commercially available cartridges should be checked for compliance with the requirements of this standard before use. Another advantage of commercially available cartridges is that they contain silica gel with a larger particle size, which results in less air pressure drop in the cartridge. These low pressure drop cartridges can be useful for sampling air in the breathing zone with battery powered pumps.
R is alkyl or aromatic for ketones, or H for aldehydes; R" is an alkyl or aromatic group for ketones.
Figure 1 - Scheme of the reaction of carbonyl compounds with DNPH
4. Restrictions and interfering substances
4.1. General provisions
The requirements of this standard have been confirmed by sampling air for a flow rate of not more than 1.5 l/min. This flow limitation is due to the high pressure drop (greater than 8 kPa at a flow rate of 1.0 L/min) through a user-prepared silica gel cartridge with a particle size of 55 to 105 µm. These cartridges are not compatible with battery powered pumps used for air sampling in the breathing zone (eg for industrial hygiene purposes). For sampling and analysis of air samples to determine the content of formaldehyde in it, a specific sampling technique for a solid sorbent is used. Difficulties may arise in the implementation of the method due to the presence of some isomers of aldehydes or ketones, which cannot be separated by HPLC when analyzing other aldehydes and ketones. Interfering substances are also organic compounds that have the same retention time and significant absorption at a wavelength of 360 nm as DNPH, a derivative of formaldehyde. The influence of interfering substances can be eliminated by changing the separation conditions (eg using different HPLC columns or changing the composition of the mobile phase). Often there is a problem of contamination of DNPH with formaldehyde. In such cases, DNPH is purified by repeated recrystallization from acetonitrile, pure in the UV region of the spectrum. Recrystallization is carried out at a temperature of 40 °C to 60 °C by slowly evaporating the solvent to obtain crystals maximum size. The content of impurities of carbonyl compounds in DNPH is preliminarily determined by HPLC, and it should be no more than 0.15 μg per cartridge. Sampling cartridges coated with DNPH should not be exposed to direct sunlight to avoid side peaks [4]. This method is not used to accurately quantify acrolein in air. Inaccurate results of the quantitative determination of acrolein may be due to the appearance of several peaks of its derivatives and instability of peak ratios [5]. NO 2 reacts with DNPH. High content MO 2 (for example, when using gas stoves) can lead to problems, since the retention time of its DNPH - derivative can coincide with the retention time of DNPH - a formaldehyde derivative, depending on the HPLC column and analysis parameters [ 6], [ 7], [ eight].4.2. Interfering effect of ozone
Special measures should be taken if high levels of ozone in the air are expected in the sampling area (eg from office copiers). The presence of ozone leads to an underestimation of the result of determining the content of analytes, since in the cartridge it reacts with both DNPH and its derivatives (hydrazones) [9]. The degree of interference depends on changes in ozone and carbonyl content over time, as well as on the duration of sampling. A significant underestimation of the determination result (negative interfering effect of ozone) was observed even at the mass concentrations of formaldehyde and ozone corresponding to pure atmospheric air (2 and 80 µg/m3, respectively) [10]. During the analysis, the presence of ozone in the sample can be judged by the appearance of new compounds, the retention time of which is less than the retention time of formaldehyde hydrazone. Figure 2 shows chromatograms of formaldehyde-enriched air with and without ozone. The simplest solution to reduce the disturbing effect of ozone is to remove it before the bleed air reaches the cartridge. This can be achieved by using an ozone trap or an ozone scrubber upstream of the cartridge. Commercially available ozone traps and scrubbers are used. Also, an ozone trap can be made from a copper tube 1 m long, with an outer diameter of 0.64 cm and an inner diameter of 0.46 cm, which is filled with a saturated aqueous solution of potassium iodide, left for several minutes (for example, 5 minutes), then the solution is drained and the tube dry in a stream of clean air or nitrogen for about 1 hour. The throughput of such an ozone remover is about 200 µg/m 3 per hour. The analyzed aldehydes (formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and n-toluyl aldehyde), introduced into the bleed air flow in dynamic mode, passed through the ozone trap almost without loss [11]. Commercially available ozone scrubbers, which are cartridges filled with granular potassium iodide weighing from 300 to 500 mg, are also effective for removing ozone [12].
X - unknown connection; 0 - DNPH; 1 - formaldehyde; 2 - acetaldehyde; a - with ozone; b - no ozone
Figure 2 - Examples of chromatograms for formaldehyde in an air stream with and without ozone
5. Safety requirements
5.1. This standard does not specify all the safety requirements that should be observed in its application. The user of the standard must develop appropriate safety and health measures, taking into account the requirements of legislative acts. 5.2. DNPH is explosive when dry and must be handled with extreme care. It is also toxic, has been shown to be mutagenic in some tests, and is an eye and skin irritant. 5.3. Perchloric acid less than 68% by mass is stable and does not oxidize at room temperature. However, it is easily dehydrated at temperatures above 160°C, which can lead to an explosion when it comes into contact with alcohols, wood, cellulose and other oxidizable materials. It should be stored in a cool, dry place and used with extreme caution only in a fume hood.6. Equipment
In addition to conventional laboratory equipment, the following equipment is used. 6.1. Sampling 6.1.1. Sampling cartridge, filled with silica gel, coated with DNPH, prepared in accordance with Section 8 or commercially available. The cartridge must contain at least 350 mg of silica gel, and the mass fraction of DNPH deposited on it must be at least 0.29%. The ratio of the silica gel layer diameter to its thickness should not exceed 1:1. The load capacity of the formaldehyde cartridge must be at least 75 μg, and the collection efficiency must be at least 95% at an air flow of 1.5 l/min. Sampling cartridges are commercially available with low blank levels and high performance. NOTE At an air flow of 1.5 l/min, it has been observed that the pressure drop in the user-prepared cartridge is approximately 19 kPa. Some commercially available DNPH pre-coated cartridges have a lower pressure drop, allowing battery-operated pumps to be used for breathing zone sampling. 6.1.2. Air sampling pump providing accurate and precise flow in the range of 1.0-1.5 l/min. 6.1.3. A flow regulator, flow meter, flow regulator or similar device for measuring and regulating the air flow through the sampling cartridge in the range of 0.50 - 1.20 l/min. 6.1.4. Flow calibrator, such as a rotameter, soap foam bubble flow meter or liquid seal drum gas meter. 6.2. Sample preparation 6.2.1. Cartridge containers, borosilicate glass tubes (20 to 125 mm long) with polypropylene screw caps, or other containers suitable for transporting loaded cartridges. 6.2.2. Polyethylene gloves for carrying silica gel cartridges. 6.2.3. Shipping containers, metal boxes (4 liter capacity) with airtight lid or other suitable containers with air bubble plastic wrap or other suitable aggregate to hold and cushion the impact of the sealed cartridge containers. Note—The sample cartridges are stored in the heat-sealed, foil-lined plastic bag supplied with commercially available DNPH-coated cartridges. 6.2.4. Device for applying DNPH to cartridges The syringe rack is an aluminum plate (0.16 × 36 × 53 cm) with four adjustable legs. A plate with round holes (number of holes - 5 × 9), with a diameter slightly larger than the diameter of 10 ml syringes, symmetrically located from the center of the plate, allows cleaning, application of DNPH and/or sample elution for 45 cartridges (see Figure 3) .
a - a device for applying DNPH; b - device for drying cartridges; 1_ glass syringe with a capacity of 10 ml; 2 - rack for syringes; 3 - cartridges; 4 - drain glass; 5 - stream N 2 ; 6 - fitting for syringes; 7 - cup for waste
Figure 3 - Devices for applying DNPH and drying sample cartridges
6.2.5. Cartridge dryer with gas inlets and multiple fittings for standard syringes (see Figure 3). NOTE The apparatus specified in 6.2.4 and 6.2.5 is only necessary if the user fabricates DNPH 6.3 coated cartridges. Sample analysis 6.3.1. The HPLC system consists of a mobile phase vessel, a high pressure pump, an injection cock (automatic dispenser with a loop volume of 25 µl or other suitable loop volume), a C-18 reverse phase column (e.g., 25 cm long, 4.6 in. mm, filler particle size 5 µm), a UV or diode array detector operating at a wavelength of 360 nm, a data processing system or an electrical recorder. DNPH-formaldehyde derivative is determined by reverse phase HPLC in isocratic eluent mode on the basis of the readings of the UV absorption detector operating at a wavelength of 360 nm. The blank cartridges are desorbed and analyzed in the same way. Formaldehyde and other carbonyl compounds in a sample are identified and quantified by comparing their retention time and peak height or area obtained from sample analysis and calibration solutions. NOTE Most commercial HPLC analytical systems are suitable for this purpose. 6.3.2 Syringes and pipettes 6.3.2.1. HPLC injection syringes with a capacity of at least four times the volume of the loop (see 6.3.1). 6.3.2.2. Syringes with a capacity of 10 ml, used for applying DNPH to cartridges (polypropylene syringes are allowed). 6.3.2.3. Fittings and plugs used to connect cartridges to the sampling system and close prepared cartridges. 6.3.2.4. Automatic pipette dispenser operating on the principle of positive displacement, multiple dosing with a variable volume in the range from 0 to 10 ml (hereinafter referred to as pipette dispenser).
7. Reagents
7.1. DNPH recrystallized at least twice before use from acetonitrile, pure in the UV region of the spectrum. 7.2. Acetonitrile, pure in the UV region of the spectrum (each portion of the solvent must be checked before use). 7.3. Perchloric acid, solution with a mass fraction of 60%, ρ = 1.51 kg / l. 7.4. Hydrochloric acid, solution with a mass fraction from 36.5% to 38%, ρ = 1.19 kg / l. 7.5. Formaldehyde (formalin), solution with a mass fraction of 37%. 7.6. Aldehydes and ketones, of high purity, used to prepare calibration samples for DNPH derivatives (optional). 7.7. Ethanol or methanol for chromatography. 7.8. High purity nitrogen. 7.9. Charcoal granulated charcoal (highest quality). 7.10. High purity helium (highest quality).8. Preparation of reagents and cartridges
8.1. Purification of 2,4-dinitrophenylhydrazine
The problem of formaldehyde contamination of DNPH is quite common. Purification of DNPH is carried out by repeated recrystallization from acetonitrile, which is pure in the UV region of the spectrum. Recrystallization is carried out at a temperature of from 40°C to 60°C by slow evaporation of the solvent to obtain crystals of maximum size. The content of impurities of carbonyl compounds in DNPH, which is determined before analysis by HPLC, should not exceed 0.15 μg per cartridge and per individual compound. A supersaturated solution of DNPH is prepared by boiling a solution containing an excess of DNPH in 200 ml of acetonitrile for approximately 1 hour. Then, the supernatant is separated and poured into a beaker with a lid, standing on a hot plate, and gradually cooled to 40°C-60°C . Maintain the solution at this temperature (40°C) until 95% of the solvent volume has evaporated. The solution is filtered, and the remaining crystals are washed twice with acetonitrile with a volume exceeding the visible volume of the crystals by three times. Transfer the crystals to another clean beaker, add 200 ml of acetonitrile, heat to boiling, and allow the crystals to grow again on cooling to 40°C-60°C until 95% of the solvent volume has evaporated. Repeat the process of washing the crystals. Take an aliquot of the solution and dilute tenfold with acetonitrile, then acidify with 1 ml of perchloric acid (3.8 mol/l) per 100 ml of DNPH solution and analyze by HPLC in accordance with 9.3.4. Warning - Cleaning of DNFG must be carried out with the ventilation turned on with the obligatory use of explosion protection equipment (shield). NOTE An acid is required to catalyze the reaction of carbonyl compounds with DNPH. For these purposes, the most powerful inorganic acids are used, such as perchloric, sulfuric, phosphoric or hydrochloric. In rare cases, the use of hydrochloric and sulfuric acids can lead to adverse effects. The level of formaldehyde hydrazone impurities in recrystallized DNPH is considered acceptable if the mass concentration is less than 0.025 μg/ml or the mass fraction of impurities in DNPH is less than 0.02%. If the level of impurities is unacceptable for specific conditions sampling, then the recrystallization is carried out again. The purified crystals are transferred to a glass flask, 200 ml of acetonitrile are added, stoppered, shaken gently and allowed to stand for 12 hours. Analyze the supernatant on an HPLC chromatograph in accordance with 9.3.4. If the level of impurities is unacceptable, then pipette all the supernatant solution, then add 25 ml of acetonitrile to the remaining purified crystals. Repeat the washing of the crystals with acetonitrile in portions of 20 ml; after each addition of a portion of acetonitrile, the resulting supernatant is analyzed by HPLC until an acceptable level of impurities in the supernatant is confirmed. If the impurity level is acceptable, add 25 ml of acetonitrile, stopper the flask, shake and leave for later use. The resulting saturated solution over purified crystals is the main stock solution of DNPH. Maintains the minimum volume of saturated solution required for daily use, minimizing wastage of purified reagent when rewashing crystals is required to reduce impurities when more stringent purity requirements are required. The volume of the basic initial saturated solution of DNPH required for the analysis is taken with a clean pipette. Do not pour the stock solution directly from the flask.8.2. Preparation of DNPH derivative of formaldehyde
Sufficient hydrochloric acid (2 mol/l) is added to a portion of the recrystallized DNPH to obtain an almost saturated solution. Formaldehyde (formalin) is added to this solution in a molar excess with respect to DNPH. The precipitate of DNPH derivative of formaldehyde is filtered, washed with hydrochloric acid (2 mol/l) and water and left in air until dry. Check the degree of purity of DNPH-derived formaldehyde by determining its melting point (from 165°C to 166°C) or analysis by HPLC. If the level of impurities is unacceptable, the derivative is recrystallized from ethanol. Repeat the purity check and recrystallization until an acceptable level of purity is achieved (eg 99 wt % main component). DNPH derivative of formaldehyde is stored refrigerated (at a temperature of 4°C) in a place protected from light. It should be stable for at least 6 months. Storage under nitrogen or argon extends the shelf life of the DNPH derivative. The melting points of DNPH derivatives of some carbonyl compounds are given in Appendix B. DNPH derivatives of formaldehyde and other carbonyl compounds used as reference materials are commercially available both as pure crystals and as individual or mixed stock solutions in acetonitrile.8.3. Preparation of stock solutions of DNPH derivative of formaldehyde
The stock solution of DNPH derivative of formaldehyde is prepared by dissolving a precisely known amount of the derivative in acetonitrile. A working calibration solution is prepared from the initial solution. The content of DNPH-derived formaldehyde in calibration solutions should correspond to the expected range of its mass concentration in real samples. Stock solutions with a mass concentration of approximately 100 mg/l can be prepared by dissolving 10 mg of the solid derivative in 100 ml of acetonitrile. These solutions are used to prepare calibration solutions containing the corresponding derivatives in the mass concentration range from 0.5 to 20 µg/ml. Store all standard solutions protected from light in sealed vials in the refrigerator. Before use, the solutions are kept at room temperature until thermal equilibrium is reached. After four weeks, the solutions should be replaced with fresh ones.8.4. Preparation of cartridges coated with silica gel DNPH
8.4.1. General provisions The procedure is carried out in a laboratory with a very low content of aldehydes in the air. All glass and plastic laboratory glassware is thoroughly cleaned and rinsed in deionized water and aldehyde-free acetonitrile. Contact of reagents with air in the laboratory should be kept to a minimum. Polyethylene gloves should be worn when handling cartridges. 8.4.2. DNPH application solution Pipette 30 ml of a saturated DNPH stock solution into a 1000 ml volumetric flask, add 500 ml of acetonitrile and acidify with 1.0 ml of concentrated hydrochloric acid. The air above the acidified solution is filtered through a silica gel cartridge coated with DNPH to minimize the introduction of contamination from the laboratory air into the solution. Shake the flask, then make up to the mark with acetonitrile. The flask is closed, inverted, shaken several times until the solution becomes homogeneous. Transfer the acidified solution to a pipettor with a scale of 0 to 10 ml. From the dispenser, slowly pour from 10 to 20 ml of the solution into a drain glass. Inject an aliquot of the solution into the vial and check the level of impurities in the acidified solution by HPLC in accordance with 9.3.4. The mass concentration of formaldehyde in the solution should be no more than 0.025 µg/ml. 8.4.3. Application of DNPH on silica gel in a cartridge Remove the cartridge from the package, connect the short end of the cartridge to a 10 ml syringe, which is placed in the DNPH application device as shown in Figure 3a). Using a pipette dispenser, 10 ml of acetonitrile is injected into each syringe. The liquid should drain off by itself. Air bubbles that appear between the syringe and the silica gel cartridge are removed with acetonitrile from the syringe. Adjust the pipette dispenser containing the acidified DNPH application solution to inject 7 ml into each cartridge. As soon as the flow of acetonitrile stops at the exit of the cartridge, 7 ml of the solution for applying DNPH is added to each syringe. The DNPH application solution flows by gravity through the cartridge until flow stops at the other end of the cartridge. Excess fluid at the outlet of each cartridge is removed with filter paper. Carry out the assembly of the device for drying the cartridges (see figure 3 b). A pre-prepared DNPH coated cartridge (e.g. scrubber or "protective" cartridge) is installed at each outlet. These "guard" cartridges are designed to remove traces of formaldehyde that may be present in the nitrogen supply. They are prepared by drying several newly impregnated cartridges according to the instructions below and used to ensure that the remaining cartridges are clean. Mount the cartridge adapter (flared at both ends, 0.64 to 2.5 cm OD, made of fluorocarbon tubing, with an ID slightly smaller than the outer diameter of the cartridge inlet) to the long end of the "protective" cartridge. Disconnect the cartridges from the syringes and connect the short ends of the cartridges to the free ends of the adapters already attached to the "protective" cartridges. Nitrogen is passed through each cartridge at a flow rate of 300-400 ml/min. Wash the outer surfaces and outlet ends of the cartridges with acetonitrile using a Pasteur pipette. After 15 minutes, the nitrogen supply is stopped, acetonitrile residues are removed from the outer surfaces of the cartridges, and the dried cartridges are disconnected. Both ends of the loaded cartridges are sealed with standard polypropylene syringe caps and the closed cartridges are placed in borosilicate glass tubes with polypropylene screw caps. Each individual glass cartridge storage container is marked with a batch and batch number and the entire batch is stored in the refrigerator until use. It has been established that the contents of the loaded cartridges remain stable for at least 6 months. at storage at a temperature of 4 °C in the place protected from light.9. Methodology
9.1. Sample selection
Assemble the sampling system and verify that the pump provides constant flow throughout the sampling period. Loaded cartridges may retain their sampling performance if the ambient temperature is above 10°C. If necessary, install a scrubber or ozone trap (see 4.2). Before starting sampling, check the tightness of the system. Close the inlet (short) end of the cartridge so that there is no air flow at the pump outlet. In this case, the flow meter should not record the air flow through the sampling system. During unattended or long sampling periods, it is recommended to use a flow regulator or a pump with a flow compensation function for sampling in the breathing zone to maintain a constant air flow. The flow regulator is adjusted so that the flow value is at least 20% below the set maximum air flow through the cartridge. Note - The silica gel in the cartridge is held between two fine filters. The air flow during sampling may change due to the deposition of aerosol particles on the front filter. The change in flow can be significant when sampling air with a high concentration of suspended particles. Install the sampling system (including the blank sample cartridge) and check the airflow at a value close to expected. Usually the air flow is set in the range of 0.5 - 1.2 l/min. The total number of moles of carbonyl compounds in the volume of sampled air should not exceed the amount of DNPH in the cartridge (2 mg or 0.01 mol; 1 to 2 mg if using commercially available pre-loaded cartridges). Typically, an estimate of the mass of analyte in the sample should be less than 75% of the mass of DNPH loaded into the cartridge [100 to 200 µg in the case of HCHO, including interfering substances (see section 4)]. Graduation is carried out using a soap-foam bubble flow meter or a drum gas meter with a liquid seal connected to the flow outlet, provided that the system is tight. Note - A calibration method that does not require the tightness of the system after the pump is given in [13]. To determine the sample volume, fix and record the flow rate at the beginning and end of the sampling period. If the sampling period is more than 2 hours, then the flow rate is measured several times during sampling. To monitor the flow rate without interfering with the sampling process, a rotameter is installed in the system. It is also possible to use a sampling pump with direct measurement and continuous recording of flow rates. Before sampling begins, the loaded cartridge is removed from a sealed metal or other suitable shipping container. Before connecting to the flow driver (aspirator, pump), the cartridge is kept at room temperature until thermal equilibrium is reached, without removing it from the glass container. Commercially available preloaded cartridges are subjected to the same procedure. Putting on polyethylene gloves, take out the plug of the cartridge and connect it to the flow stimulator using an adapter. The cartridge is connected in such a way that its short end is the inlet end for the sample. Connection of commercially available cartridges with pre-coated DNPH is carried out in accordance with the manufacturer's instructions. Some commercially available cartridges are sealed glass tubes. In this case, it is necessary to break off the ends of the tube with the preliminary use of a glass cutter. Connect the end of the cartridge with less sorbent to the sampling line so that more sorbent is at the air sample inlet. Be careful when handling broken tube ends. Turn on the pump and set the required flow rate. Typically, the flow through one cartridge is 1.0 l/min, and in the case of two cartridges connected in series, 0.8 l/min. Sampling is carried out for a specified period of time, while periodically fixing the values of the sampling parameters. If the ambient temperature is below 10° C. during sampling, ensure that the sampling cartridge is at a higher temperature. When sampling in different weather conditions - in cold, wet and dry winter months, in hot and humid summer months - no significant effect of relative air humidity on the sampling results was noted. At the end of sampling, turn off the pump. Immediately before turning it off, check the air flow. If the air flow values at the beginning and end of the sampling period differ by more than 15%, then the sample is marked as doubtful. Immediately after sampling, the cartridge is disconnected from the sampling system (wearing polyethylene gloves), stoppered, and placed back into the labeled container. Seal the container with fluoroplastic tape and place it in a metal container containing a layer of 2 to 5 cm thick granular charcoal, or in another suitable container with an absorbent. If necessary, a heat-sealed plastic bag with foil interlayers is used to store the sample cartridge. Before analysis, the sample cartridge is stored in a refrigerator. The storage time of the cartridge in the refrigerator should not exceed 30 days. If the sample needs to be transported for analysis analytical laboratory, then the storage time of the sample cartridge without refrigeration should be kept to a minimum and not exceed two days. The average sampling flow rate q A, ml/min, is calculated by the formulaq A = / n , (1)
Where q 1 , q 2 , ... q n - flow rates at the beginning, intermediate points and end of sampling; n- number of averaging points. The total volume of air V m , l, taken at a known temperature and pressure during sampling, is calculated by the formula
V m \u003d (T 2 - T 1) q A / 1000, (2)
Where T 2 - end time of sampling; T 1 - start time of sampling; T 2 - T 1 - duration of sampling, min; q A - average flow, ml / min.
9.2. blank samples
For each series of samples, analyze at least one blank sample obtained under sampling conditions. If the series includes 10 - 20 samples, then the number of blank samples should be at least 10% of the total number of samples. To determine the required number of blank samples, the total number of samples within a series or time interval should be recorded. At the sampling site, blank sampling cartridges are handled in the same way as actual sampling cartridges, with the exception of the sampling process itself. Blank sampling shall comply with the requirements given in 9.1. It is also desirable to analyze blank cartridges left in the laboratory to distinguish between contamination that may be introduced at the sampling site and in the laboratory.9.3. Sample analysis
9.3.1. Sample preparation Samples are transported to the laboratory in a suitable container containing a layer of 2 to 5 cm thick granulated charcoal and stored in a refrigerator until analysis. Samples can also be stored in individual containers. The time interval between sampling and analysis of samples should be no more than 30 days. 9.3.2. Sample desorption Connect the sample cartridge with the short end (inlet) to a clean syringe. To prevent insoluble particles from entering the eluate, the direction of liquid flow during desorption should be the same as the direction of air flow during sampling. If the eluate is filtered prior to HPLC analysis, back desorption can be performed. For each batch of samples, the filtered net extract is analyzed to confirm that the filter is free of contaminants. The syringe with the attached cartridge is placed on the syringe rack. Desorption of DNPH-derivatives of carbonyl compounds and unreacted DNPH is carried out, allowing 5 ml of acetonitrile to drain from the syringe by gravity through the cartridge into a graduated test tube or volumetric flask with a capacity of 5 ml. Depending on the sampling cartridge used, other volumes of acetonitrile may be injected. Note - The free volume of the dry silica gel cartridge is slightly over 1 ml. The flow of eluate may stop before all the acetonitrile flows out of the syringe into the cartridge due to the presence of air bubbles between the cartridge filter and the syringe. In this case, air bubbles are removed by injecting acetonitrile into the syringe using a long Pasteur pipette. The solution was diluted with acetonitrile to the mark of 5 ml. The flask is labeled in the same way as the sample. An aliquot is pipetted into a vial with a fluorocarbon membrane. An aliquot is analyzed for the content of DNPH derivatives of carbonyl compounds by HPLC. A second aliquot may be taken as a backup and stored in the refrigerator until the assay is completed and a valid assay of the first aliquot is obtained. If necessary, a second aliquot is used for a confirmatory assay. When using sealed glass tubes containing two layers of sorbent coated with DNPH for sampling, break off the end of the tube that is closer to the second layer of sorbent (outlet end). Carefully remove the spring and glass wool plug holding the sorbent layer. Pour the sorbent into a clean 4 ml glass vial with a fluorocarbon membrane or cap. The vial is labeled as a spare part of the sample. Carefully remove the second stopper from glass wool and pour the remaining sorbent into another vial with a capacity of 4 ml. The vial is labeled as the main part of the sample. Add 3 ml of acetonitrile to each vial with a pipette, close the vials and leave for 30 min, during which the vials are periodically shaken. 9.3.3. HPLC calibration Calibration solutions are prepared by dissolving the DNPH derivative of formaldehyde (see 8.3) in acetonitrile. Prepare individual stock solutions with a mass concentration of 100 mg/l by dissolving 10 mg of the solid derivative in 100 ml of the mobile phase. Each calibration solution is analyzed twice (at least five different values of mass concentration) and a table is made of the dependence of the values of the output signals corresponding to the area of chromatographic peaks on the input mass of the corresponding substance (or, more conveniently, on the input mass of DNPH derivative of formaldehyde at fixed loop volume (see figures 4 and 5)). During the calibration, operations are performed corresponding to the operations carried out during the analysis of the sample and established in 9.3.4. To avoid the memory effect of the chromatograph, the analysis begins with the solution with the lowest mass concentration. When using a UV detector or a detector based on a diode array, a linear dependence of the output signal should be obtained when introducing solutions with a mass concentration in the range of 0.05 - 20 µg/ml with an injected volume of 25 µl. The results obtained are used to construct a calibration graph (see Figure 6). The calibration characteristic (dependence of the output signal corresponding to the peak area on the mass concentration value) obtained by the least squares method is considered linear if the correlation coefficient is not less than 0.999. The retention times for each analyte should not differ from each other by more than 2%. After establishing a linear calibration characteristic, its stability is checked daily using a calibration solution with a mass concentration value close to the expected value of each component, but not less than 10 times the detection limit. The relative change in the output signal, determined by daily checking, should not exceed 10% for analytes with a mass concentration of at least 1 µg/ml and 20% for analytes with a mass concentration of approximately 0.5 µg/ml. If a greater change is observed, it is necessary to re-calibrate or build a new calibration graph based on freshly prepared calibration solutions.
Chromatography conditions: column: C-18 reverse phase; mobile phase: with a volume ratio of 60% acetonitrile/40% water; detector: UV detector operating at a wavelength of 360 nm; flow rate: 1 ml/min; retention time: for DNPH derivative of formaldehyde approximately 7 minutes; injected sample volume: 25 µl.
Figure 4 - An example of a chromatogram of DNPH - a derivative of formaldehyde
Chromatography conditions: column: C-18 reverse phase; mobile phase: with a volume ratio of 60% acetonitrile/40% water; detector: UV detector operating at a wavelength of 360 nm; flow rate: 1 ml/min; retention time: for DNPH derivative of formaldehyde approximately 7 minutes; injected sample volume: 25 µl.
Figure 5 - Examples of chromatograms of DNPH-formaldehyde derivative at its various mass concentrations
Chromatography conditions: correlation coefficient: 0.9999; column: C-18 reversed phase; mobile phase: with a volume ratio of 60% acetonitrile/40% water; detector: UV detector operating at a wavelength of 360 nm; flow rate: 1 ml/min; retention time: for DNPH derivative of formaldehyde approximately 7 minutes; injected sample volume: 25 µl;
Figure 6 - Example of a calibration curve for formaldehyde
9.3.4. Formaldehyde analysis by HPLC Assemble and calibrate the HPLC system in accordance with 9.3.3, typical of the system being: column: C-18, 4.6 mm ID, 25 cm long, or equivalent; it is not necessary to control the column temperature; mobile phase: 60% acetonitrile/40% water (v/v), isocratic; detector: UV detector operating at a wavelength of 360 nm; flow rate: 1.0 ml/min; retention time: for DNPH-formaldehyde derivative 7 min using one C-18 column, 3 min using two C-18 columns; injection volume: 25 µl. Before each analysis, check the baseline of the detector to ensure stable conditions. Prepare a mobile phase for HPLC by mixing 600 ml of acetonitrile and 400 ml of water, or set appropriate parameters for gradient elution. The resulting mixture is filtered through a polyester membrane filter with a pore size of 0.22 μm in a vacuum filtration device made only of glass or PTFE. Degas the filtered mobile phase by purging with helium for 10 to 15 min (100 ml/min) or by heating to 60°C for 5 to 10 min in a laboratory conical flask covered with a watch glass. To prevent the formation of gas bubbles in the detector cell, a constant resistance limiter (350 kPa) or a short (15–30 cm) PTFE tube with an internal diameter of 0.25 mm is installed after it. The mobile phase is poured into the solvent container and the flow rate is set to 1.0 ml/min. Before the first analysis, the pump should run for 20 - 30 minutes. The detector is turned on at least 30 minutes before the start of the first analysis. The output signal of the detector is recorded using electrical recorders or a similar output device. For systems with manual sampling, draw at least 100 µl of sample into a clean injection syringe to inject into the chromatograph. Fill the loop of the dosing valve with the mobile phase (the dosing valve must be set to the “loading” position), adding the excess sample using a syringe. To start chromatography, the metering valve is moved to the “sample injection” position. Simultaneously with the input, the data processing system is activated, the input point is turned on and marked on the chart tape of the electric measuring self-recording instrument. After approximately 1 min, move the dosing valve from the “sample injection” position to the “loading” position, rinse or rinse the syringe and dosing loop with a mixture of acetonitrile and water to prepare for the analysis of the next sample. It is not allowed to introduce solvent into the loop of the dosing valve when the valve is in the “sample injection” position. After elution of the DNPH formaldehyde derivative (see Figure 4), stop recording data and calculate the mass concentration of the components in accordance with section 10. The system can be used for further analysis of samples after a stable baseline is reached. NOTE After several analyses, contamination of the column (as evidenced, for example, by an increase in pressure with each subsequent injection at a given flow rate and solvent composition) can be eliminated by washing it with 100% acetonitrile with a volume exceeding the volume of the column several times. Similar protection can be provided using precolumns. If the value of the mass concentration of the analyte goes beyond the linear section of the calibration characteristic of the system, the sample is diluted with the mobile phase or a smaller sample volume is introduced into the chromatograph. If the retention times obtained from previous injections are not reproducible (tolerance ± 10%), then the acetonitrile-water ratio can be increased or decreased to obtain an appropriate retention time. If the retention time is too long, then the ratio is increased; if too little - the ratio is reduced. If it is necessary to change the solvent, recalibrate before introducing the sample (see 9.3.3). NOTE The chromatographic conditions given should be optimized for the determination of formaldehyde. The analyst is encouraged to conduct studies with an existing HPLC system to optimize chromatography conditions for a particular analytical problem. HPLC systems with automatic sample injection and data collection can also be used. The resulting chromatogram is examined for ozone interference according to 4.2 and Figure 2. 9.3.5 Analysis of other aldehydes and ketones by HPLC 9.3.5.1. General Optimization of chromatographic conditions by using two C-18 columns connected in series and eluent gradient mode allows analysis of other aldehydes and ketones taken from the air. In particular, chromatography conditions are optimized to separate acetone, propionaldehyde, and some other higher molecular weight aldehydes in an analysis time of approximately 1 hour. The composition of the mobile phase is changed periodically in a linear gradient program to obtain maximum separation of C3, C4, and benzaldehyde in the appropriate region of the chromatogram. . For this purpose, the following gradient program has been developed: at the time of sample injection, the volume ratio of solutions is changed from 60% acetonitrile/40% water to 75% acetonitrile/25% water within 36 minutes; up to 100% acetonitrile - within 20 minutes; 100% acetonitrile - within 5 minutes; change direction of linear gradient programming from 100% acetonitrile to 60% acetonitrile/40% water within 1 min; maintain a volume ratio of 60% acetonitrile/40% water for 15 minutes. 9.3.5.2. Analysis of samples for other carbonyl compounds Assemble and calibrate the HPLC system in accordance with 9.3.3. Typical for the system will be: column: two C-18 columns connected in series; mobile phase: acetonitrile/water; linear gradient mode; detector: UV detector operating at a wavelength of 360 nm; flow rate: 1.0 ml/min; gradient program: according to 9.3.4. The chromatography conditions above have been optimized for gradient HPLC systems with a UV or diode array detector, an autosampler with a 25 µl loop volume, two C-18 columns (4.6 x 250 mm) and an electrical recorder or electronic integrator. The analyst is encouraged to conduct studies on an existing HPLC system in order to optimize chromatography conditions for a particular analytical problem. Optimization is required at least for the separation of acrolein, acetone and propionaldehyde. NOTE Column manufacturers usually provide recommendations for optimal conditions separation of DNPH derivatives for reverse phase columns. These recommendations may eliminate the need to use two columns without impairing the separation of carbonyl compounds. Carbonyl compounds in the sample are determined qualitatively and quantitatively by comparing their retention time and peak area with those for reference samples of DNPH derivatives. Formaldehyde, acetaldehyde, acetone, propionaldehyde, cretonaldehyde, benzaldehyde and o-, m-, p-toluyl aldehydes are determined with a high degree of reliability. The determination of butyric aldehyde is less reliable due to its co-elution with isobutyraldehyde and methyl ethyl ketone under the chromatographic conditions stated above. A typical chromatogram obtained with an HPLC system with gradient elution is shown in Figure 7. The mass concentration of individual carbonyl compounds is determined according to 9.3.4.
|
Peak identification |
Compound |
Mass concentration, μg / ml |
Formaldehyde | Acetaldehyde | Acrolein | Acetone | propionaldehyde | Crotonaldehyde | Butyaldehyde | Benzaldehyde | Isovaleraldehyde | Valeraldehyde | o - Toluylaldehyde | m - Toluylaldehyde | l - Toluylaldehyde | Hexanal | 2 , 5- D and methyl l benzaldehyde |
Figure 7 - Example of chromatographic separation of DNPH - derivatives of 15 carbonyl compounds
10. Calculation of measurement results
The total mass of the analyte (DNPH derivative) for each sample is calculated by the formulam d= m s - m b , (3)
Where m d is the corrected mass of DNPH derivative extracted from the cartridge, μg; m s is the uncorrected mass of the sample cartridge, μg:
m s= A s( c std/ A std) V s d s; (4)
m b is the mass of the analyte in the blank sample cartridge, μg:m b= A b( c std/ A std) V b d b; (5)
A s is the peak area of the analyte eluted from the sample cartridge, conventional units; BUT b is the peak area of the analyte eluted from the blank sample cartridge, conventional units; A std is the area of the analyte peak in the calibration solution for daily calibration, conventional units; c std - mass concentration of the analyte in the calibration solution for daily calibration, m kg / ml; V s is the total volume of the eluate obtained for the sample cartridge, ml; V b is the total volume of the eluate obtained for the blank cartridge, ml; d s is the dilution factor of the sample eluate: 1 if the sample was not diluted again; V d/ V a if the sample was diluted so that the output signal was in the linearity region of the detector, where V d - volume after dilution, ml; V a - aliquot used in dilution, ml; d b is the blank dilution factor equal to 1.0. The mass concentration of a carbonyl compound with A , ng/l, in the sample is calculated by the formulac A = m d( M c/ M der)1000/ V m , (6)
Where M c is the molecular weight of the carbonyl compound (for formaldehyde it is 30); M der is the molecular weight of the DNPH derivative (for formaldehyde it is 210); V m - the total volume of the air sample of the closed room, taken according to 9.1, l. Note - It is not recommended to use ppm and ppm. However, for the convenience of some users, the volume ratio of carbonyl compound ca in parts per billion (ppb) is calculated by the formula
c A= c As ∙ 24.4/ M c , (7)
The total volume of the air sample V s , l, reduced to a temperature of 25 ° C and a pressure of 101.3 kPa, is calculated by the formulaV s = (( V m ρ A)/101.3)(298/(273 + T A)), (8)
Where ρ A - average atmospheric pressure inside the enclosed space, kPa; T A - average ambient temperature in a closed room, °C. If it is necessary to express the content of the analyte in parts per million (ppm) under standard ambient conditions (temperature 25°C and pressure 101.3 kPa) for comparison with reference samples, the composition of which is set to the same values, the sampled volume should not be reduced to standard conditions.
11. Performance criteria and quality control of measurement results
11.1. General provisions
This section establishes the measures necessary to ensure the quality control of the measurement results and guidance on meeting the performance criteria that must be met. The user of the standard must comply with the requirements of ISO 9001, ISO 17025.11.2. Standard Operating Procedures
The user of the standard should develop standard operating procedures for the following activities in the laboratory: assembly, calibration and use of the sampling system, indicating the manufacturer and model of the equipment used; preparation, purification, storage and processing of reagents used in sampling and the samples themselves; assembly, calibration and use of the HPLC system, indicating the brand and model of the equipment used; method of recording and processing data, indicating the hardware and software tools COMPUTER. The description of standard operating procedures should include step-by-step instructions and be accessible and understandable to personnel working in the laboratory. Standard operating procedures shall comply with the requirements of this standard.11.3. HPLC System Efficiency
The efficiency of the HPLC system is determined by the column efficiency η (number of theoretical plates), which is calculated by the formulaη = 5.54( t r /w 1/2) 2 , (9)
Where t r is the retention time of the analyte, s; w 1/2 - peak width for one component at half height, s. The column efficiency should be at least 5000 theoretical plates. The relative standard deviation of the output signal during repeated daily injections of samples into the HPLC system should not exceed ±10% for calibration solutions with an analyte mass concentration of at least 1 µg/mL. When the mass concentration of some carbonyl compounds is not more than 0.5 µg/ml, the precision of repeated analyzes can increase up to 20%. Retention time precision should be within ±7% on any given day of analysis.
11.4. Sample Loss
Sample loss is observed when the allowable sorbent load is exceeded or if the volume flow exceeds the maximum allowable for the sampling system used. Sample loss can be prevented by installing two sampling cartridges connected in series and then analyzing the contents of each, or by installing a two-section sorbent cartridge and then analyzing both sections. If the amount of analyte in the spare section is more than 15% of the amount of analyte in the main section, a "breakthrough" is assumed and the accuracy of the results is questioned.12. Precision and uncertainty
As with the analysis of other compounds, two factors affect the precision and uncertainty of the result of determining the content of formaldehyde in indoor air: the reproducibility of the analytical procedure and the change in the content of the analyte in the air over time. The latter factor is considered to be much more influential than the former, although it is difficult to quantify the effect of changes in source intensity and ventilation conditions. General information on error values related to the analytical procedure is given in Annex A.Annex A
(reference)
Precision and Uncertainty
A methodology similar to the analysis methodology given in this International Standard has been evaluated. The precision related to the analytical procedure should be within ± 10% for an analyte mass concentration of at least 1 µg/mL. At a mass concentration of not more than 0.5 μg / ml, the precision in repeated analyzes of some carbonyl compounds can increase up to 25%. A method using silica gel cartridges (particle size 55 to 105 µm) coated with DNPH was evaluated in the round trip [14] - [16] similar to the method specified in this International Standard. The results of the assessment below can be used to evaluate the effectiveness of the use of this method for the analysis of air of the closed rooms. Two different laboratories have used the cartridges to carry out more than 1500 measurements of formaldehyde and other carbonyl compounds in atmospheric air as part of a research program in 14 US cities [15], [16]. The precision of 45 repeated injections of the calibration solution of DNPH, a formaldehyde derivative, into the HPLC system for 2 months, expressed as a relative standard deviation, was 0.85%. Based on the results of a triplicate analysis of each of the 12 identical samples from the DNPH-coated cartridges, the values of the formaldehyde content were obtained, which are consistent within a relative standard deviation of 10.9%. 16 laboratories of the USA, Canada and Europe took part in the circular tests. During these tests, 250 cartridges with blank samples, three sets of 30 cartridges with three values of the content of injected DNPH derivatives and 13 series of cartridges exposed to vehicle exhaust gases [14] - [16] were analyzed. Cartridges meeting the requirements of 4.2 were prepared by one laboratory. All samples were randomly assigned to the laboratories participating in the round robin. The results of the circuit tests are summarized and given in Table A.1. NOTE The round robin test did not use a standardized HPLC analysis procedure. The participants in the trials used the HPLC-based methods they use in practice in their laboratories. The absolute value of the difference, expressed as a percentage, between the results of two series of measurements (sampling from the same place) carried out under the US research program in 1988, was 11.8% for formaldehyde (n = 405), acetaldehyde - 14 .5% (n = 386) and acetone - 16.7% (n = 346) [15], [16]. As a result of the analysis of two samples taken almost at the same point within the framework of this program for formaldehyde content by another laboratory, the relative standard deviation was 0.07, the correlation coefficient was 0.98, and the uncertainty was minus 0.05 for formaldehyde [15]. The corresponding values for acetaldehyde were 0.12; 0.95 and minus 0.50, and for acetone - 0.15; 0.95 and minus 0.54 [16]. An analysis of the cartridges after injection of DNPH into them, conducted by one laboratory over the course of a year, showed that the average uncertainty was 6.2% for formaldehyde (n = 14) and 13.8% for acetaldehyde (n = 13). Analysis of 30 cartridges after injection of DNPH into them by one laboratory under this program showed that the average uncertainty was 1.0% (range - 49% to + 28%) for formaldehyde and 5.1% (range - minus 38% to minus 39%) for acetaldehyde. Table A.1 — Results of round trip tests |
Sample type |
Formaldehyde |
Acetaldehyde |
propionaldehyde |
Benzaldehyde |
Blank cartridges: | aldehyde, mcg | rsd, % | n | Sample Cartridge 3): | degree of extraction, % (rsd , %) | short | average | tall | n | Samples in environment with car exhaust gases: | aldehyde, mg | rsd, % | n | a) Low, medium and high levels of aldehyde introduced into the cartridge were approximately 0.5; 5 and 10 mcg, respectively. Note - 16 laboratories took part in the studies. Values were derived from a data series after outliers were removed from it. Designations used in the table: rsd - relative standard deviation; n is the number of measurements. |
Annex B
(reference)
Melting points of DNPH derivatives of carbonyl compounds
Table B.1 - Melting points of DNPH derivatives of carbonyl compounds |
Name of the carbonyl compound |
Melting point of DNPH derivative [17], °C |
Acetaldehyde | 152 to 153 (168.5 [ 18], 168 [ 19]) | Acetone | 125 to 127 (128[ 18], 128[ 19]) | Benzaldehyde | 240 to 242 (235 [ 19]) | Butyaldehyde | 119 to 120 (122 [ 19]) | Cretonaldehyde | 191 to 192 (190 [ 19]) | 2,5-dimethylbenzaldehyde | 216.5 to 219.5 | Formaldehyde | 166 (167 [ 18], 166 [ 19]) | Hexanaldehyde | 106 to 107 | Isovaleraldehyde | 121.5 to 123.5 | propionaldehyde | 144 to 145 (155 [ 19]) | o - Toluylaldehyde | 193 to 194 (193 to 194 [19]) | m - Toluylaldehyde | 212 (212 [ 19]) | n - Toluylaldehyde | 234 to 236 (234 [ 19]) | Valeraldehyde | 108 to 108.5 (98 [ 19]) |
Appendix C
(reference)
Information on the compliance of the national standards of the Russian Federation with reference international standards
Table C.1 |
Reference international standard designation |
Designation and name of the corresponding national standard |
ISO 9001:2000 | GOST R ISO 9001-2001 Quality management systems. Requirements | ISO 16000-1:2004 | GOST R ISO 16000-1-2007 Indoor air. Part 1. Sampling. General provisions | ISO 16000-2:2004 | GOST R ISO 16000-2-2007 Indoor air. Part 2. Sampling for formaldehyde content. Key points | ISO 16000-4:2004 | GOST R ISO: 16000-4-2007 Indoor air. Part 4. Determination of formaldehyde. Diffusion sampling method | ISO/IEC 17025:2005 | GOST R ISO / IEC 17025-2006 General requirements for the competence of testing and calibration laboratories | * There is no corresponding national standard. Prior to its approval, it is recommended to use the Russian translation of this International Standard. The translation of this international standard is in the Federal Information Fund of Technical Regulations and Standards. |
Bibliography
| Method TO-11A, EPA-625/R-96-010b, Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air, U.S. Environmental Protection Agency, Cincinnati, OH, 1996 | Air Quality Guidelines for Europe. Copenhagen: WHO Regional Office for Europe. WHO Regional Publications. European series No. 23/1987 | Revised values see webpages: | www.who.int.peh, www.who.dk/envhlth/pdf/airqual.pdf | Tejada, S. B., Evaluation pf silica gel cartridges coated in situ with acidified 2,4-dinitrophenylhydrazine for sampling aldehydes and ketones in air, Int. J. Environ. Anal. Chem., 26, 1986, pp. 167 - 185 | Grosjean, D., Ambient levels of formaldehyde, acetaldehyde, and formic acid in southern California: Results of a one-year baseline study, Environ. sci. Technol., 25, 1991, pp. 710 - 715 | J.-O. Levin and R. Lindahl, Aldehyde measuring methods using DNPH-coated filters - Summary and conclusions, Proc. Workshop "Sampling Project", 27 - 28 June, 1996, Mol, Belgium | VDI 3862 Part 2 | Gaseous Emission Measurement - Measurement of Aliphatic and Aromatic Aldehydes and Ketones - DNPH Method - Impinger Method | VDI 3862 Part 3 | Gaseous Emission Measurement - Measurement of Aliphatic and Aromatic Aldehydes and Ketones - DNPH Method - Cartridges Method | A. Sirju and P.B. Shepson, Laboratory and field investigation of the DNPH cartridge technique for the measurement of atmospheric carbonyl compounds, Environ. sci. Technol., 29, 1995, pp. 384 - 392 | Arnts, R.R., and Tejada, S. B., 2,4-Dinitrophenylhydrazine-coated silica gel cartridge method for determination of formaldehyde in air: Identification of an ozone interference, Environ. sci. Technol., 23, 1989, pp. 1428 - 1430 | Sirju, A., and Shepson, P.B. Laboratory and field evaluation of the DNPH cartridge technique for the measurement of atmospheric carbonyl compounds, Environ. sci. Technol., 29, 1995, pp. 384 - 392 | R.G. Merrill, Jr., D-P. Dayton, P.L. O"Hara, and R.F. Jongleux, Effects of ozone removal on the measurement of carbonyl compounds in ambient air: Field experience using Method TO- 11, in Measurement of Toxic and Related Air Pollutants, Vol. 1, Air & Waste Management Association Publication VIP -21, Pittsburgh, PA, U.S.A., 1991, pp. 51-60 | T.E. Kleindienst, E.W. Corse, F.T. Blanchard, and W.A. Lonneman, Evaluation of the performance of DNPH-coated silica gel and C1 8 cartridges in the measurement of formaldehyde in the presence and absence of ozone, Environ. sci. Technol., 32, 1998, pp. 124 - 130 | EN 1232:1997 | Workplace atmospheres - Pumps for personal sampling of chemical agents - Requirements and test methods | ASTM D51 97-97 Standard Test Method for Determination of Formaldehyde and Other Carbonyl Compounds in Air (Active Sampler Methodology), Annual Book of ASTM Standards, 11.03, American Society for Testing and Materials, West Conshohoken, PA, U.S.A. , pp. 472 - 482 | USEPA, 1989 Urban airtoxics monitoring program: Formaldehyde results, Report No. 450/4-91/006. U.S. Environmental Protection Agency, Research Triangle Park, NC, U.S.A., January 1991 | USEPA, 1990 Urban Air Toxics Monitoring Program: Carbonyl Results, Report No. 450/4-91/025, U.S. Environmental Protection Agency, Research Triangle Park, NC, U.S.A., July 1991 | Certificate of Analysis, Radian International, Austin, TX, U.S.A | Handbook of Chemistry and Physics, CRC, 18901 Cranwood Parkway, Cleveland, OH, U.S.A | Organikum, Organisch-chemisches Grundpraktikum, Wiley-VCH, Weinheim, Germany |
Group K29
INTERSTATE STANDARD
FURNITURE, WOOD AND POLYMER MATERIALS
Method for determining the emission of formaldehyde and other harmful volatiles
chemical substances in climatic chambers
Furniture, timber and polymers.
Method for determination of formaldehyde and other volatile chemicals in
the air of climatic chambers
OKS 79.97.140
Introduction date
Foreword
1 DEVELOPED by the All-Russian Design and Technological Institute of Furniture (VKTIM), the All-Russian Research Institute of the Woodworking Industry (VNIIDrev) and the Scientific and Practical Center for Hygienic Expertise of the State Committee for Sanitary and Epidemiological Supervision of Russia
INTRODUCED by the Technical Secretariat of the Interstate Council for Standardization, Metrology and Certification
2 ADOPTED by the Interstate Council for Standardization, Metrology and Certification
|
State name |
Name of the national standardization body |
|
Republic of Belarus |
Belstandard |
|
The Republic of Moldova |
Moldovastandard |
|
The Republic of Kazakhstan |
State Standard of the Republic of Kazakhstan |
|
State Standard of Ukraine |
|
|
the Russian Federation |
Gosstandart of Russia |
3 Decree of the Russian Federation Committee for Standardization, Metrology and Certification dated 23.08.95 N 448 interstate standard GOST was put into effect directly as the state standard of the Russian Federation on July 1, 1996
4 INTRODUCED FOR THE FIRST TIME
1 AREA OF USE
This standard establishes a method for determining the release of formaldehyde and other harmful volatile substances into the air in climatic chambers from furniture products, chipboard and fibreboard, plywood, parts and blanks from them, parquet products, as well as polymer, structural materials used in their manufacture. , facing, finishing and adhesive materials.
GOST 8.207-76 GSI. Direct measurements with multiple observations. Methods for processing the results of observations. Key points
GOST 1770-74 Measuring laboratory glassware. Cylinders, beakers, flasks, test tubes. Specifications
GOST 3117-78 Acetic ammonium. Specifications
GOST 3118-77 Hydrochloric acid. Specifications
GOST Soluble starch. Specifications
GOST Acetylacetone. Specifications
GOST Furniture. General specifications
GOST Armchairs for auditoriums. General specifications
GOST Furniture for sitting and lying. General specifications
GOST Furniture for educational institutions. Specifications
3 TESTING EQUIPMENT AND ACCESSORIES
3.1 Climatic chambers with working space volume from 0.12 to 50 m
3.1.1 The design of the chamber must ensure tightness, automatic control of temperature, humidity. For lining the inner surfaces of the chamber, materials with a low sorption capacity (stainless metal, glass) should be used.
3.1.2 The ventilation system should provide uniform air circulation throughout the entire working volume of the chamber with the installed samples.
3.1.3 The following parameters must be maintained in the working volume of the chamber during the tests:
air temperature - (23±2) °С;
relative air humidity - (45±5)%;
air exchange per hour - 1±0.1.
The test of parquet products is carried out with air exchange (0.5 ± 0.05) per hour.
3.2 Aspirating device with a flow meter to determine the speed or volume of air.
3.3 Absorption devices such as Polezhaev, Richter, with porous plates.
3.4 Chromatographs, spectrophotometers, electrophotocolorimeters that provide determination of the content of a volatile chemical in the sampled air (selected depending on the type of substance being determined).
3.5 Laboratory scales with the maximum weighing limit of 500 g with a weighing error of ±0.02 g.
3.6 Analytical balances with a maximum weighing limit of 200 g with a weighing error of ±0.0005 g.
3.7 Aneroid barometer.
3.8 Stopwatch with a division of the second scale of 0.2 s.
3.9 Psychrometer or other device for monitoring temperature and humidity.
3.10 Universal measuring tools for measurement of the sizes of samples with an error of ±1 mm.
3.11 Measuring instruments, auxiliary means, materials, chemical reagents, laboratory glassware - in accordance with the methods for determining harmful volatile chemicals approved by the sanitary and epidemiological authorities.
4 SAMPLE COLLECTION AND PREPARATION
4.1 To test furniture products, samples are taken in an amount that creates a given saturation of the chamber volume:
For cabinet furniture, tables, beds - 1 m of sample surface area per 1 m of climate chamber volume;
For furniture products for sitting and lying - 0.3 m of sample surface area per 1 m of climate chamber volume.
The surface area of the samples is calculated with an error of ±3%. It includes the total area from 2 sides of all furniture parts (surfaces of the rear walls, the bottom of drawers, shelves, surfaces behind mirrors, plugs in furniture for sitting and lying, etc.).
As a rule, furniture products selected for physical and mechanical testing in accordance with the requirements of GOST 16371, GOST 19917, GOST 22046, GOST 16854 are subjected to tests in a climatic chamber.
4.2 To test parts and blanks, parquet products, as well as structural, facing, finishing and adhesive materials, at least 3 samples are taken, made in accordance with the technical documentation.
4.2.1 Paints and varnishes are applied to the surface of glass, tin or wood according to the consumption rates used in the production of materials, parts and products.
4.2.2. Adhesive materials are applied to the surface of glass, tin or wood according to the consumption rates used in production, and a sample of the material for which the adhesive is intended is glued.
4.2.3 Samples of wood-based panels and plywood are taken from the zone of the board, spaced from its edges at a distance of at least 300 mm.
4.2.4 Samples of polymeric and facing materials are presented with dimensions that create a given saturation.
4.2.5 The area of the sample (over layers on both sides) intended for testing in chambers with a volume of 0.12 to 1 m inclusive, is calculated with an error of ±3%, based on the saturation of 1 m of the surface area of the sample per 1 m of the chamber volume.
The area of samples of parquet products is determined only from the front side. Saturation for parquet products is taken equal to 0.4 m of sample surface area per 1 m of chamber volume. The dimensions of the samples in length and width are determined based on the internal dimensions of the climatic chambers.
4.2.6 If the emission of harmful volatile chemicals through the sheets is being assessed, then the edges of the samples should have an airtight protective coating (edge plastic, aluminum foil glued with silicate glue, etc.).
The edges of parquet samples are not protected.
4.2.7 Transportation and storage of samples - in accordance with the regulatory documents for the tested products, materials.
4.3 Testing of samples made with adhesives or adhesive joints is carried out no earlier than 7 days after their manufacture, unless otherwise specified in regulatory documents.
Before testing, furniture items made of wood and wood-based materials are kept for at least 3 days in a room with a relative humidity of 45 to 70% and a temperature of 15 to 30 °C.
4.4 Samples submitted for testing must be accompanied by a passport containing their characteristics (Appendix A).
5 TESTING
5.1 Preparing for the test
5.1.1 Testing of chipboard, fibreboard, plywood, parts and blanks from them, parts of parquet products, structural, facing, finishing, polymeric and adhesive materials is carried out in climatic chambers with a volume of 0.12 to 1 m inclusive.
Testing of furniture products is carried out in chambers with a volume of more than 1 m , allowing to place these products in accordance with the specified conditions.
5.1.2 The samples are placed in the chamber on a stand or in another way that provides free air circulation, while the contact area should not exceed 0.5% of the sample surface area.
5.1.3 Samples of parquet products are placed on the floor of the chamber, the front surface of the samples must be turned up. It is allowed to install samples in another way, while their non-working surface must be protected by a gas-tight material (foil, etc.).
5.1.4 Furniture items are placed in the chamber, evenly distributing them over the floor area. Products must be located at a distance of at least 0.1 m from each other and from the walls of the chamber. The doors of the products must be opened at an angle of at least 30 °, the drawers extended at least a third of their length.
5.1.5 In chambers with a volume of more than 1 m (Figure 1), fix the tubes for air sampling and connect them to the appropriate outlet openings of the chamber.
In chambers up to 1 m inclusive, air sampling can be carried out through one outlet.
5.1.6 After placing the samples, seal the chamber doors tightly. The air conditioning and ventilation system is turned on, and after reaching the specified parameters, the automatic mode of operation of the chamber is set.
The control of the working parameters of the air is carried out by the instruments included in the design of the chamber, and by a control device operating autonomously.
5.2 Testing in chambers up to 1 m inclusive
5.2.1 Throughout the test, air sampling from the working volume of the chamber is carried out with a given frequency.
The first air sampling is carried out 24 hours after the stabilization of the air parameters in the chamber in accordance with the requirements of 3.1.3. The second, third and subsequent selections are carried out every 24 hours for 5 days from the start of the test.
5.2.2 In this case, when the results of three consecutive samplings establish that the concentration of volatile substances in the chamber is constant (i.e., the standard deviation of the measurement results is not more than 15%), the test is stopped before the expiration of 5 days.
5.2.3 Simultaneously with sampling from the climatic chamber, the air supplied to the chamber is taken.
5.2.4 Air sampling is carried out using an aspiration device (3.2) and absorption devices (3.3), selected depending on the type of controlled substances and the method for determining their concentration.
5.2.5 Air samples are analyzed on the day of sampling in accordance with the methods for measuring the concentration of harmful volatile chemicals approved by the sanitary and epidemiological authorities. To determine the concentration of harmful volatile chemicals, use photoelectrocolorimeters, spectrophotometers or chromatographs of any type that provide the necessary resolution and measurement error (3.4 and 3.5).
5.2.6 The method for determining formaldehyde with an acetylacetone reagent (colorimetric method) is given in Appendix B. A spectrophotometer or photoelectrocolorimeter is used to determine the concentration of formaldehyde.
5.2.7 The measurement results are recorded in the work log.
5.3 Testing furniture products in chambers with a volume of more than 1 m
5.3.1 The first air sampling from the chamber and control air sampling at the entrance to the chamber is carried out 72 hours after the establishment of the operating mode of the air in the chamber.
5.3.2 Subsequent air sampling is carried out every 24 hours.
5.3.3 In the event that, based on the results of three consecutive samplings, it is established that the concentration of controlled volatile substances is constant (the standard deviation of the measurement results does not exceed 15%), the test is terminated.
After 21 days, the test is terminated regardless of the value of the concentration of controlled volatile substances.
5.3.4 Air sampling is carried out at six points shown in Figure 1, located at two levels of chamber height.
I- air sampling levels (750; 1500 mm); // - tubes for sampling
air from the chamber; 1 ; 2; 3; 4; 5; 6 - air sampling points
Picture 1
At each level, three points are determined, evenly distributed along the length and width of the chamber.
It is allowed to take air samples from a smaller number of points, but not less than two, located at different height levels.
5.3.5 Air sampling and analysis is carried out in accordance with 5.2.3-5.2.7.
6 PROCESSING OF TEST RESULTS
6.1 The concentration of volatile chemicals in the climate chamber air in milligrams per cubic meter is calculated in accordance with the methods for measuring controlled substances (5.2.5).
6.2 The absolute value of the concentration of the volatile chemical released by the test sample into the air of the climatic chamber is calculated by the formula
where is the concentration of a volatile substance in the air of the climatic chamber, mg/m;
The concentration of a volatile substance in the air entering the chamber, mg/m.
6.3 The value of the concentration of a volatile chemical released into the air of a climatic chamber up to 1 m inclusive, is found as the arithmetic mean of the test results of at least three samples according to the formula
where is the number of observation repetitions.
6.4 The standard deviation of the measurement results, %, is determined by the formula
. (3)
6.5 The concentration of the volatile chemical at each measurement made in accordance with 5.3.1, 5.3.2 and 5.3.4 in chambers larger than 1 m3 , is determined as the arithmetic mean of the measurement results at different points of the chamber according to the formula (2).
6.6 The final value of the concentration of a harmful volatile chemical in climatic chambers with a volume of more than 1 m when testing furniture products is calculated as an arithmetic mean () measurement results for the last three air samplings, calculated by formulas (1) and (2). The standard deviation is determined by the formula (3).
In the case when the concentration of a substance is constant (5.3.3) in three consecutive measurements, the arithmetic mean value is taken as a characteristic of the controlled parameter.
In the case when the concentration of a substance is not constant (decreases or increases), the concentration value obtained during the last selection and calculated by formula (1) is taken as a characteristic.
6.7 Evaluation of the test results is carried out by comparing them with the maximum permissible concentrations harmful substances in the atmospheric air, duly approved by the bodies of the State Sanitary and Epidemiological Surveillance.
6.8 Samples are considered to have passed the test if the results obtained are less than or equal to the standards established in the regulatory documents for products.
6.9 The test results are documented in a protocol (Appendix B).
The form of the passport of the sample submitted for testing
PASSPORT
|
name of the sample, product, furniture set, project, designation, |
|
|
index (if available) |
|
|
Name of the manufacturer (customer) | |
|
Sample production date | |
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Name of regulatory documentation for products | |
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for products and materials |
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Characteristics of the samples:
The sample was made using the following materials:
1 slab
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Material name |
Designation (brand) according to ND |
formaldehyde emissions perforator |
sample size, |
Note* |
chipboard
fibreboard
* If necessary, the type of binder and other characteristic features of the sample are indicated.
2 Facing materials, flooring and other polymeric materials
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Material name |
Designation of normative documentation |
Basic chemical composition (if necessary) |
sample size, |
Intelligence about permission for use |
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Material name |
Designation of normative documentation |
sample size, |
Intelligence about permission material for use |
Note - Depending on the type and purpose of the test, other information is given in agreement with the testing laboratory.
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Signatures of the head of the customer and the person responsible for communication with the testing laboratory (center), transcript of signatures, date |
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APPENDIX B
(mandatory)
FORMALDEHYDE DETERMINATION METHOD
WITH ACETYLACEtone REAGENT
B.1 FIELD OF APPLICATION
This method is designed to determine the concentration of formaldehyde in the air of residential premises and climatic chambers.
B.2 ESSENCE AND CHARACTERISTICS OF THE METHOD
The method is based on the reaction of the interaction of formaldehyde with an acetylacetone reagent in an ammonium acetate medium with the formation of a yellow-colored product.
The lower limit of detection of formaldehyde is 0.001 mg in 10 cm3 of the analyzed solution.
Determination error ±10%.
The range of measured concentrations of formaldehyde in the atmospheric air, the air of enclosed spaces and climatic chambers is from 0.008 to 1.3 mg/m3 with air sampling of at least 120 dm3.
The determination of formaldehyde does not interfere with methyl and ethyl alcohols, ethylene glycol, hydrogen sulfide, ammonia.
B. H MEASURING INSTRUMENTS AND AUXILIARY DEVICES
B.3.1 Aspirating device providing an air flow rate of 2 dm/min.
B.3.2 Spectrophotometer or photoelectric colorimeter with a light filter with a maximum light absorption at a wavelength of 412 nm and a cuvette with a working layer width of 10 mm.
B.3.3 Volumetric flasks 50, 250 and 1000 cm3 according to GOST 1770.
B.3.4 Conical flasks 100 cm in accordance with GOST 1770.
B.3.5 Absorption devices such as Polezhaev, Richter.
B.4 REAGENTS AND SOLUTIONS
B.4.1 Acetylacetone, analytical grade according to GOST 10259.
B.4.2 Acetic acid, glacial x. h.
B.4.3 Ammonium acetate, analytical grade according to GOST 3117.
B.4.4 Formalin, 40% formaldehyde solution.
B.4.5 Caustic soda, analytical grade 30% solution.
B.4.6 Hydrochloric acid, conc. h.d.a according to GOST 3118, diluted 1:5.
B.4.7 Sodium sulfate NSO fixanal, 0.1N solution.
B.4.8 Iodine, fixanal 0.1 N solution.
B. 4.9 Soluble starch according to GOST 10163, 1% solution.
B.4.10 Acetylacetone reagent: 200 g of ammonium acetate are dissolved in 800 ml of water in a 1 dm volumetric flask. 3 cm3 of acetylacetone and 5 cm3 of acetic acid are added to the solution, and the solution in the flask is brought to the mark with water (absorbing solution).
B.4.11 Initial solution for calibration: 5 cm3 of formalin are added to a 250 cm3 volumetric flask and made up to the mark with water. Then determine the content of formaldehyde in this solution. To do this, 5 cm of the solution is placed in a 250 cm conical flask with a ground stopper, 20 cm of 0.1 N iodine solution is added and a 30% sodium hydroxide solution is added dropwise until a stable pale yellow color appears. The flask is left for 10 minutes, then a solution of 2.5 ml of hydrochloric acid (diluted 1:5) is carefully acidified, left for 10 minutes in the dark, and the excess iodine is titrated with a 0.1 N solution of sodium thiosulfate. When the solution turns light yellow, add a few drops of starch. Pre-set the amount of thiosulfate consumed for titration of 20 cm 0.1 N iodine solution. By the difference in the amount spent for the control titration and the excess of iodine that did not react with formaldehyde, the amount of iodine used for the oxidation of formaldehyde is determined. 1 cm 0.1 N iodine solution corresponds to 1.5 mg formaldehyde. Having established the content of formaldehyde in 1 cm 3 of the solution, prepare the initial and working solutions of formaldehyde with a content of 0.1 mg/cm and 0.01 mg/cm, respectively, by appropriate dilution with water. The content of formaldehyde in solutions is determined titrimetrically.
B.5 SAMPLING
B.5.1 When tested in climatic chambers polymer materials and products, sample preparation and sampling procedures are carried out in accordance with sections 4 and 5 of this standard.
B.5.2 To determine the maximum single concentration of formaldehyde in the air of a climatic chamber or an enclosed space, air is aspirated at a speed of 2 dm3/min in a volume of 60-120 dm distilled water. During the sampling process, a non-volatile derivative of formaldehyde is formed.
B.5.3 At the same time, a control sample of the air supplied to the climatic chamber is taken.
Sampling is carried out in accordance with 5.2.
B.6 ANALYSIS PROCEDURE
B.6.1 The selected samples are placed in a water bath heated to 40 °C and kept for 30 minutes.
B.6.2 After cooling the samples, the optical density of colored solutions is measured using a spectrophotometer or photoelectrocolorimeter at a wavelength of 412 nm in cuvettes with a working layer width of 10 mm. Evaluation of the quantitative content of formaldehyde in the sample is carried out according to the calibration characteristic.
B.7 SETTING THE CALIBRATION CHARACTERISTICS
B.7.1 Into a 10 cm volumetric tube with a 2 cm pipette, add a working solution of formaldehyde (B.4.11), water with a 5 cm pipette, dilute with an absorbing solution to the mark, and prepare solutions for calibration in accordance with Table B.1 (when determining low formaldehyde concentrations) and Table B.2 (when determining high formaldehyde concentrations).
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Solutions, cm | ||||||||
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Working solution of formaldehyde with a content of 0.01 mg/cm | ||||||||
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Acetylacetone reagent |
7 cm in each tube |
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Note - When preparing solutions 1 and 2, use a capillary pipette or an automatic microdoser.
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Solutions, cm |
Numbers of solutions for graduation |
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Formaldehyde stock solution containing 0.1 mg/cm | ||||||||
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Acetylacetone reagent |
7 cm in each tube |
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B.7.2 Solutions for calibration are heated in a water bath for 30 minutes at T - 40 °C, cooled and measured in them optical density (wavelength is 412 nm, the width of the working layer of the cuvette is 10 mm). - atmospheric pressure, mbar;
- air sample volume, m;
The optical density of the analyzed sample, calculated as the difference between the sum of the optical densities of the analyzed solutions in 2 absorbers and the zero (blank) solution;
0.00371 - coefficient of reduction to normal conditions.
Test report form
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name of the accredited testing laboratory (center) |
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number and date of the accreditation certificate in the GOST R certification system |
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postal address and telephone number of the testing laboratory (center) |
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APPROVE Head of the testing laboratory (center) | |||||||||||||||||
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full name | |||||||||||||||||
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PROTOCOL N |
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type of test |
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name and designation of the tested samples |
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1 Manufacturer | |||||||||||||||||
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name and address |
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2 Date of manufacture and sampling | |||||||||||||||||
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3 Basis for testing | |||||||||||||||||
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number and date of the letter |
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(contract) of the customer |
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4 Designation of regulatory documentation for products | |||||||||||||||||
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5 Measured indicators | |||||||||||||||||
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list of defined |
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controlled indicators |
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6 List (designation) of regulatory documents |
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on test methods | |||||||||||||||||
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7 List of certified test equipment | |||||||||||||||||
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designation, number and date of the certificate (certificate, brand) |
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8 Sample characterization | |||||||||||||||||
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9 Test conditions | |||||||||||||||||
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temperature and relative |
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humidity in the chamber, saturation, air exchange |
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10 Test results | |||||||||||||||||
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text or tables |
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with reference values |
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11 Conclusion | |||||||||||||||||
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Artists' signatures |
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position |
full name |
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The text of the document is verified by:
official publication
M.: IPK Standards Publishing House, 1995
Methodical instructions.
Formalin - aqueous solution of formaldehyde (35-40%). It is a colorless transparent liquid with a characteristic odor; when stored in a chilled state, formalin becomes cloudy with the formation of a precipitate. For disinfection, a solution is prepared with a certain content of formaldehyde in formalin.
Before disinfection, it is necessary to check the percentage of formaldehyde in the solution. Usually a formaldehyde solution is prepared from formalin containing 35-40% formaldehyde. For example, to prepare a 4% formaldehyde solution from an existing 40% formalin, you must first compose the next proportion:
100: 40 \u003d x: 4, from where x \u003d 100 ∙ 4 / 40 \u003d 10
The found value means that to obtain a 4% formaldehyde solution, you need to take 10 ml of the available 40% formalin and 90 ml of water.
For each batch of formalin, there must be a passport, which indicates the name of the drug, the name of the plant, the mass and percentage of formaldehyde.
Formalin is used to disinfect livestock facilities. It can be used in aqueous solutions, gaseous state (steam-formalin chambers, aerosols) both in pure form and in mixtures with other chemicals. The bactericidal action is based on the ability of formaldehyde to denature microbial proteins.
Exercise 1.Determination of the percentage of formaldehyde in formalin (titration method)
Glassware and reagents: 500 ml conical flask, burettes, normal sodium hydroxide solution, decinormal iodine solution, decinormal sodium thiosulfate solution, hydrochloric acid - 1 N. solution, 1% starch solution.
Definition progress: 30 ml of normal sodium hydroxide solution, 50 ml of formalin diluted 20 times (95 ml of distilled water are added to 5 ml of formalin) and 100 ml of 0.1 n. iodine, which is poured from the burette in small portions, carefully mixing the poured portion of iodine with the liquid in the flask in a circular motion of the flask. The flask is then stoppered and placed in dark place for 30 minutes, after which add 40 ml of 1 N. hydrochloric acid solution. In this case, an almost colorless liquid (mixture) becomes brown. It is titrated with decinormal thiosulfate solution. When the mixture becomes slightly yellow, 1 ml of a 1% starch solution (indicator) is poured into the flask. The liquid turns blue and then becomes colorless as the titration continues. The percentage of formaldehyde in formalin is determined by the formula:
x \u003d (100 - y) ∙ 0.0015 ∙ 20 ∙ 20,
100 is the amount of iodine solution, ml;
y is the amount of thiosulfate used for titration, ml;
0.0015 - gram equivalent of formaldehyde;
20 - dilution of formalin;
20 is a multiplier for converting to a percentage.
Task 2. Determination of formaldehyde in formalin by density
Glassware and reagents: a glass cylinder of 0.5 or 1 l, a densimeter with divisions of 1.08-1.16, the tested formalin (should have a temperature of 18 ... 20 0 C).
Definition progress: formalin is poured into a glass cylinder up to ⅔ of its height and its density is determined with a densimeter. The percentage of formaldehyde is calculated by the formula:
x \u003d 1000 (D - 1) / 2.5,
D is the density of formalin;
1 - water density;
1000 - multiplier for converting fractional numbers into an integer;
2.5 is a constant.
Dry formalin(paraform) contains 95-96% formaldehyde. It is a powder white color. To obtain a solution of 1% concentration, take 1 part of dry formalin and 99 parts of water (for a 3% concentration, respectively, 3 parts of powder and 97 parts of water, etc.). Water must be heated to 50 ... 60 0 C.
Dry formalin solutions are used for disinfection in the same order and at the same concentrations as formaldehyde solutions.
Parasode and phospar are white powders, highly soluble in hot water (50...60 0 C), stable during storage. They are prepared on the basis of paraform, sodium carbonate and trisodium phosphate and contain 50% paraform. They have high bactericidal and virucidal properties. For wet disinfection, 3-4% solutions of parasode and fospar are used.
To obtain solutions of this concentration, take 3 or 4 kg of one of the drugs, respectively, gradually add 50 liters hot water(50 ... 60 0 С), stirring until complete dissolution, then add cold water to obtain 100 liters of disinfectant.
With the aerosol method, parasode and fospar are used in the form of 40% solutions at the rate of 30 ml per 1 m 3 of the room. To prepare 40% solutions, take 40 kg of one of the preparations per 100 liters of water.
Formaldehyde determination method
a common part
The technique is designed to determine the concentration of formaldehyde in the atmospheric air settlements in the range of 0.01 - 0.3 mg/m 3 with a sample volume of 20 dm 3 . Used to measure single concentrations.
The method is based on the capture of formaldehyde from the air with a solution of sulfuric acid and its photometric determination by the colored compound formed as a result of the interaction of formaldehyde with phenylhydrazine hydrochloride and chloramine B in an acidic environment.
Preparation of solutions
1 Distilled water. When measuring formaldehyde concentrations in atmospheric air, freshly prepared distilled water is used.
2 Iodine, solution 0.05 mol / dm 3 (0.1 N). Prepared from standard titer.
3 Starch, 0.5% solution. 0.25 g of starch is mixed with 10 cm 3 of water until a uniform suspension is obtained. To 40 cm 3 of water heated to 60 - 70 ° C, a suspension of starch is added with continuous stirring, boiled for 1 minute and cooled.
4 Sulfuric acid, 20% solution. To 80 cm 3 of distilled water, carefully add 11 cm 3 of concentrated sulfuric acid.
5 Hydrochloric acid, 10% solution. To 78.1 cm 3 of distilled water, carefully add 21.9 cm 3 of concentrated hydrochloric acid.
6 Sodium hydroxide, 20% solution. 20 g of sodium hydroxide are dissolved in distilled water. The volume is adjusted to 100 cm 3 .
7 Sodium thiosulfate, solution 0.1 mol / dm 3 (0.1 N). Prepared from standard titer.
8 Phenylhydrazine hydrochloric acid, 5% solution. 5 g of phenylhydrazine hydrochloric acid is dissolved in distilled water. The volume is adjusted to 100 cm 3 . The solution is prepared on the day of analysis. In the presence of turbidity, it is filtered through a blue ribbon filter.
9 Mixture of ethanol with phenylhydrazine. To 10 cm 3 of ethanol, add 2 cm 3 of a 5% solution of phenylhydrazine and mix.
10 Chloramine B, 0.5% solution. 0.25 g of chloramine B is dissolved in distilled water. The volume is adjusted to 50 cm 3 . The solution is prepared on the day of analysis.
11 Formaldehyde stock solution (c = 10 µg/cm3). An approximately 1% solution of formaldehyde is prepared, for which 2.5 cm 3 of formalin are dissolved in water in a volumetric flask with a capacity of 100 cm 3 and then its concentration is accurately determined by iodometric titration. Having determined the concentration of formaldehyde in the solution, a solution containing 10 µg/cm 3 of the substance is prepared by appropriate dilution.
12 Formaldehyde working solution (c = 1 µg/cm3). 10 cm 3 of the stock solution (see listing 11) is diluted in a volumetric flask to 100 cm 3 with water. The solution is prepared before use.
13 Absorption solution - sulfuric acid, solution 0.005 mol / dm 3. Prepared by adding 0.27 cm 3 concentrated sulfuric acid to 1000 cm 3 distilled water.
Table 6 - Solutions for establishing the calibration characteristics when determining the concentration of formaldehyde
Establishment of the calibration characteristic
The calibration characteristic, which expresses the dependence of the optical density of the solution on the concentration of formaldehyde, is set for five series of calibration solutions. Each series, consisting of six solutions, is prepared from a freshly prepared formaldehyde solution.
Solutions for establishing the calibration characteristics are prepared in volumetric flasks with a capacity of 100 cm 3 . To do this, a working solution of formaldehyde is poured into each flask in accordance with the table. 6, dilute the volume with the absorbent solution to the mark and mix thoroughly.
To establish the calibration characteristics, 5 cm 3 of each calibration solution are taken into test tubes, 1.2 cm 3 of a freshly prepared mixture of ethanol and phenylhydrazine are added, and mixed. After 15 minutes, 1 cm 3 of a 0.5% solution of chloramine B is added and mixed again. After 10 minutes, 2 cm 3 of a 20% sulfuric acid solution are added to each sample, mixed. After 10 minutes, the optical density is measured at 520 nm with respect to water in cuvettes with a distance between the working faces of 20 mm. At the same time, the optical density of the zero solution is measured: 5 cm 3 of the absorbing solution, to which the same reagents are added. The actual values of the optical density are found by the difference between the optical densities of the calibration solutions and the zero solution.
Sample selection
To determine the single concentration of formaldehyde, the test air is aspirated through a Richter absorption device filled with 6 cm 3 of an absorption solution at a flow rate of 1 dm 3 /min for 20 minutes. The sample is analyzed on the day of collection.
Taking measurements
Transfer 5 cm 3 of the sample solution into a test tube, add 1.2 cm 3 of a freshly prepared mixture of ethanol and phenylhydrazine, mix. After 15 minutes, 1 cm 3 of a 0.5% solution of chloramine is added and mixed. After 10 minutes, 2 cm 3 of a 20% sulfuric acid solution are added to the sample and mixed again. After 10 minutes, the optical density is measured at 520 nm with respect to water in cuvettes with a distance between the working faces of 20 mm. Similarly, three zero samples are analyzed, which use 5 cm 3 of the absorbing solution. The time from adding the last reagent to measuring the optical density of all samples should be the same. The mean optical density of the zero sample should not exceed 0.04.
The mass of formaldehyde in the sample is determined using the established calibration characteristic by the difference in the optical densities of the sample solutions and the average optical density of zero samples.
The calculation of the measurement result is carried out according to the formula:
where: с - mass concentration (mg/m3) of suspended particles in the air
V a - the volume of the solution taken for analysis, cm 3
V p - the total volume of the sample solution, cm 3
V about - the volume of the air sample, reduced to n.o., dm 3.
pollution atmospheric ammonia phenol
