This standard specifies the determination of methanol and acetone concentrations in residential atmosphere by gas chromatography. This standard applies to the determination of methanol and acetone concentrations in residential atmosphere. GB/T 11738-1989 Standard method for hygienic inspection of methanol and acetone in residential atmosphere Gas chromatography GB/T11738-1989 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Gas chromatography for hygienic examination ofmethanol and acetone in air of residentialareas
Standard method
Standard method for hygienic examination ofmethanol and acetone in air of residentialareas --Gas chromatography
1 Subject content and scope of application
This standard specifies the determination of methanol and acetone concentrations in air of residentialareas by "gas chromatography. This standard is applicable to the determination of methanol and acetone concentrations in air of residentialareas. 1.1 Detection limit
GB 11738 --89
The detection limit of methanol and ketone is 2×10-3μg (inject 1.0μL sample solution). When the sampling volume is 5L, the minimum detection concentration of methanol and ketone is 0.40mg/m3. 1.2 Determination range
Inject 1.0uL methanol and ketone sample solution, the determination range is 2.0～20.0μg／mL, when the sampling volume is 5L, the determination range is 0.40～4.00mg/m2.
1.3 Interference and elimination
Methanol and ketone can be mixed with ethanol and acrylonitrile in the gas chromatography column. , n-propanol, sulfur dioxide, nitrogen oxides, etc., without interference. 2 Principle
Methanol and ketone in the air are adsorbed by the silica gel sampling tube, desorbed by water, separated by the GDX-102 chromatographic column, and determined by a hydrogen flame ionization detector. Qualitative analysis is performed by retention time and quantitative analysis is performed by peak height. 3 Reagents and materials
3.1 Silica gel: 40-60 mesh.
Silica gel activation treatment method: Inject the silica gel into 1+1 hydrochloric acid and soak it for one day, then wash it with water until there is no chlorine ion. After pouring the water, dry the silica gel at 90-100°C, and then at 200°C. Activate for 3 hours, cool, and pipette. 3.2 Methanol: chromatographically pure (content 99%). 8.3 Acetone: chromatographically pure (content 99%). 3.4 Stationary phase: GDX-102, 60-80 mesh, for gas chromatography. 3.5 Water: distilled water (without methanol and acetone). 3.6 Glass wool.
3.7 Polyurethane foam plastic (referred to as foam plastic). 3.8 Standard solution: Add about 10mL of water to a 25mL volumetric flask, weigh accurately, add 5 drops of methanol, weigh accurately again, the difference between the two weights is the weight of methanol, then add water to the scale and calculate The content of methanol in 1mL solution; take another 25mL volumetric flask and add about 10mL of water, weigh accurately, add 5 drops of acetone and weigh accurately again, the difference between the two weights is the weight of the acetone, add water to the scale, and calculate the content of the acetone in 1mL solution. Keep each in the refrigerator for use. Dilute with water before use to make a mixed standard solution containing 1mL of 0.1mg methanol and 1mL of 0.1mg acetone. Approved by the Ministry of Health of the People's Republic of China on September 21, 1989 514
Implementation on July 1, 1990
4 Instruments and Equipment
GB 11738-89
4.1 Gas chromatograph: with hydrogen flame ionization detector. 4.2 Chromatographic column: 2m long, 3mm inner diameter stainless steel tube, equipped with GDX-102. 4.3 Air sampler: flow range l0.2～1.0L/min, stable flow. When in use, use a soap film flowmeter to calibrate the flow rate of the sampling series before and after sampling. The error should be less than 5%. 4.4 Stoppered colorimetric tube: 5mL.
4.5 Micro-injection syringe: 10μL, the volume scale should be calibrated. 4.6 Silicone sampling tube: 90mm long, 4mm inner diameter glass tube, 150mg and 50mg silica gel in the front and rear sections respectively, 3mm long foam plastic in the middle and rear ends, and a small amount of glass wool in the air inlet, see the figure below. Put plastic caps on both ends of the silicone sampling tube and seal for later use.
Silicone sampling tube
1 Glass wool, 2-Glass tube, 3 Silicone; 4-Foam plastic 5 Sampling
Remove the plastic sealing caps at both ends of the silicone sampling tube, connect the outlet vertically to the air sampler, and sample 5L at a speed of 0.2L/min. After sampling, seal both ends of the sampling tube with plastic caps and record the temperature and atmospheric pressure during sampling. 6 Analysis steps
Chromatographic analysis conditions
Since chromatographic analysis conditions often vary due to different experimental conditions, the most suitable chromatographic analysis conditions for alcohols and ketones in the analysis should be formulated according to the model and performance of the gas chromatograph used. The chromatographic analysis conditions listed in Appendix A (reference) are an example. 6.2 Drawing standard curve and determining correction factors Under the same conditions as the sample analysis, draw the standard curve and determine the correction factor. 6.2.1 Drawing standard curve
Accurately pipette the mixed standard solution and use water to prepare a mixed standard solution containing methanol and ketone at 0.0, 2.0, 4.0, 8.0, 12.0, 16.0, and 20.0 μg/mL respectively. Take 1.0 μL of each concentration and inject it into the gas chromatograph for determination. Obtain the chromatographic peaks and retention times of each concentration. Do it for each concentration and measure the average peak height. Draw the standard curve with the methanol and ketone content (μg/mL) as the horizontal axis and the average peak height (mm) as the vertical axis. And calculate the slope of the [question] 1 line, and use the reciprocal of the residual ratio B [μg/(μL·mm)] as the calculation factor for sample determination.
6.2.2 Determination of correction factorwww.bzxz.net
When the instrument has poor stability, the correction factor can be obtained by single-point correction method. When determining the sample, take a blank solution and a standard solution with a concentration close to that of methanol and ketone in the sample extract, respectively, and measure the chromatographic peak height (mm) and retention time of the blank solution and the standard according to 6.2.1. Calculate the correction factor using formula (1). f=
Formula: f—correction factor, μg (μL·mm); hs——average peak height of standard solution, mm; h——average peak height of blank solution, mm;
concentration of standard solution, μg/mL.
6.3 Sample determination
GB11738—89
Remove the plastic sealing caps at both ends of the silica gel sampling tube, discard the glass wool and foam plastic at both ends of the tube, pour the two parts of silica gel into 5mL colorimetric tubes containing 1mL of water, seal them tightly, shake them slightly and extract for 20min, take 1.0μL of sample extract and enter the gas chromatograph for determination, and analyze each sample three times (the analyte should not be detected in the 50mg silica gel sample extract at the end). Calculate the average chromatographic peak height (mm). At the same time, take an unsampled silica gel sampling tube and operate it according to the sample determination steps as a blank tube for determination. Result calculation
Convert the sampling volume into the sampling volume under standard conditions according to formula (2): 7.1
V. =Vt
Formula: V.
Convert into the sampling volume under standard conditions, L; T.
273 + t
V, →—sampling volume, obtained by multiplying the sampling flow rate by the sampling time, LT. ——absolute temperature under standard conditions, 273K, t
—temperature of the sampling point during sampling, ℃,
—atmospheric pressure under standard conditions, 101.3kPaspo
atmospheric pressure of the sampling point during sampling, kPa.
7.2 Standard curve method Use formula (3) to calculate the concentration of methanol and acetone in the air: c=
Where: ℃
(h-ho) Bs
concentration of methanol and acetone in the air, mg/m3, hAverage peak height of the sample solution, mm,
h. = Average peak height of blank solution, mm, × 1000:
= Calculation factor obtained from 6.2.1, μg/(μL·mm) Bs
= Desorption efficiency determined experimentally,
= Total volume of sample solution, μL.
7.3 Calculate the methanol and acetone concentrations in the air using the single-point correction method according to formula (4): c
Where: f-
(h-ho)·f
×1000
= Correction factor obtained from 6.2.2, μg/(μL·mm) See 7.2 for other symbols.
8 Precision and Accuracy
(3)
(4)
8.1 Precision
When the methanol and acetone contents were 10~50μg, the coefficients of variation of repeated measurements in two laboratories were 4%~7% and 5%~6% respectively. 8.2 Accuracy
When the content of methanol and acetone was 10ug, the average recovery rates measured by the two laboratories were 92% and 93% respectively. 516
Chromatographic conditions
Vaporization chamber temperature: 180℃.
Detector temperature: 180℃.
Column temperature: 150℃.
Carrier gas (N2) flow rate: 55mL/min.
Hydrogen (H2) flow rate: 47mL／min.
Air flow rate: 500mL/min.
GB 11738--89
Appendix A
Chromatographic conditions and chromatograms
(reference)
A2 The chromatogram obtained according to the chromatographic conditions of A1 is shown in Figure A1. min
Al chromatogram
1 methanol, 2 ethanol, 3 ketone,
4 acrylonitrile: 5 n-propanol
Additional remarks:
This standard was proposed by the Health Supervision Department of the Ministry of Health. This standard was drafted by the Shenyang Municipal Health and Epidemic Prevention Station and the Liaoning Provincial Health and Epidemic Prevention Station. The main drafters of this standard are Hao Bailu, Zhao Jing, Li Wei, Huang Zhenzi, and Gao Guichun. This standard is interpreted by the Environmental Health Monitoring Institute of the Chinese Academy of Preventive Medicine, which is the technical unit entrusted by the Ministry of Health. 517
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