GB/T 11734-1989 Standard method for hygienic examination of methyl-1605 in the atmosphere of residential areas - Gas chromatography
Some standard content:
National Standard of the People's Republic of China
Standard method for hygienic examinationof methylparathion in air of residential areas-Gas chromatography
1 Subject content and scope of application
This standard specifies the determination of the concentration of methylparathion in air of residential areas by gas chromatography. This standard is applicable to the determination of the concentration of methylparathion in the air of residential areas. 1.1 Detection limit
GB 11734-89
When the injection volume is 10μL, the detection limit is 0.05μg／mL, and when the sampling volume is 20L, the lowest measurable concentration is 0.005mg/m3.
1.2 Determination range
The injection volume is 10μL, and the determination range is 0.05~2.0μg/mL. If 20L is sampled, the measurable concentration range is 0.005~0.20mg/m3. 1.3 Interference and elimination
Dimethoate, dichlorvos, ylthion, methyl-1605, and ethyl-1605 are separated by chromatographic columns and do not interfere with each other in determination. 2 Principle
Methyl-1605 pesticide in the air is adsorbed on silica gel, eluted with acetone, and then separated by gas chromatography column and determined by flame photometry detector. The retention time is used for qualitative analysis and the peak height is used for quantitative analysis. 3 Reagents and materials
The water used in the experiment is deionized water, and the chemical reagents used are analytically pure unless otherwise specified. 3.1 Silicone sampling tube
3.1.1 Pretreatment of silica gel: Place 2040 mesh primary silica gel in a beaker, add 1+1 sulfuric acid-nitric acid mixture, make the liquid level about 1cm higher than the silica gel surface, stir and place overnight, pour off the acid solution, wash with tap water until neutral, and then rinse with deionized water until there is no sulfate ion. Place in an oven at 1120℃ for 1 hour, then place in a high-temperature furnace at 360℃ for activation for 3 hours, cool, and store in a desiccator for use. 3.1.2 Preparation of silica gel tube: Take a glass tube with a length of 100mm and an inner diameter of 6mm, and put 0.6g of treated silica gel inside. Fix the two ends of the silica gel with glass wool weighing about 0.01g, and then seal the two ends of the glass tube with melting (see the figure below). KHEREHEEO
Silicone sampling tube
Glass woolwwW.bzxz.Net
3.2 Indole: chromatographically pure.
3.3 Chromatographic column: Weigh 0.45g DC550 and 0.27g OV-210 and dissolve them in 40mL acetone. Take another 9g Chromosorb WHP (80-100 mesh), bake at 150℃ for 4h, pour into the above acetone solution while hot, reflux at 60℃, evaporate to 10. Cool and load into the column. New Ministry of Health of the People's Republic of China approved on September 21, 1989 496
implemented on July 1, 1990
GB 11734—89
The chromatographic column should be heated to 140℃ for aging for 4h, then heated to 210℃ for aging for 8h, and finally heated to 240℃ for further aging for 24h. During aging, the carrier gas flow can be larger than that in normal operation. During aging, the detector should be disconnected from the chromatographic column to avoid contamination of the detector.
3.4 Standard solution: Accurately weigh the solid standard sample of methyl-1605, dissolve it in acetone, and prepare a stock solution containing 1mg in 1.00mL. When used, dilute it with acetone to make 1.00mL of methyl-1605 standard solution containing 1μg. 4 Instruments and equipment
4.1 Gas chromatograph: with flame photometric detector. 4.2 Air sampling Sampler: Flow range 0.2~1L/min, stable flow. When in use, use a soap film flowmeter to calibrate the flow before and after sampling of the sampling series. The flow error should be less than 5%. 4.3 Stoppered colorimetric tube: 10mL.
4.4 Microsyringe: 10μL (volume scale should be calibrated). 5 Sampling
Take a silicone sampling tube and cut off both ends. The opening diameter of the end connected to the sampler should be smaller than the inner diameter of the glass tube. Sample 10~20L at a flow rate of 0.5L/min. After sampling, stopper both ends of the sampling tube and store it in a dark place. Record the air temperature and atmospheric pressure at the sampling point.
6 Analysis steps
6.1 Chromatographic analysis conditions||tt| |Since chromatographic analysis conditions often vary due to different experimental conditions, the best chromatographic analysis conditions for analyzing methyl-1605 should be formulated based on the model and performance of the gas chromatograph used. The chromatographic analysis conditions listed in Appendix A (reference) are only an example. 6.2 Drawing of standard curve and determination of calculation factors 6.2.1 Drawing of standard curve: Inject 10μL of reagent blank and methyl-1605 standard solution with concentrations of 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0μg/mL into the chromatographic column respectively to obtain the chromatographic peaks and retention times at each concentration point. Make three measurements at each concentration point to obtain the average peak height. Use concentration (μg/mL) as the horizontal axis and average peak height (mm ) as the ordinate, draw a standard curve. Calculate the slope of the regression curve, and use the reciprocal of the slope Bs [μg (mL·mm)] as the calculation factor for sample determination. 6.2.2 Determination of correction factor: When the instrument stability is poor, the correction factor can be calculated by the single-point correction method. While the sample is being determined, take a blank solution and a standard solution with a concentration of methyl 1605 close to that in the sample solution, and perform chromatographic determination according to 6.2.1 to obtain the average peak height of the blank and the standard (mm). Calculate the correction factor using formula (1): co
Where:
f—correction factor, μg/(mL·mm), Co——concentration of standard solution, μg/mL, hs and ho—average peak height of the standard and blank, mm. 6.3 Sample determination
(1)
Analyze the sample under the same conditions as those for making the standard curve or correction factor. Transfer the sampled silica gel, together with the glass wool at one end of the air inlet, to a 10mL colorimetric tube, add 2.0mL acetone for extraction, and place for 10min, shaking at any time. After clarification, take 10μL of the supernatant and perform chromatographic determination according to 6.2.1, measure the peak height of methyl-1605, and determine the qualitative properties by retention time. Perform three determinations on each sample and calculate the average peak height (mm). Take another unsampled silica gel sampling tube and perform blank tube determination according to the same operating steps. 7 Result calculation
7.1 Convert the sampling volume into the sampling volume under standard conditions according to formula (2): 497
GB 11734-89
V. =Vt
273 +1
Where: V. ——Converted into sampling volume under standard conditions, L, Vt-
Sampling volume, L,
-Absolute temperature under standard conditions, 273K,
Air temperature at the sampling point during sampling, ℃,
Atmospheric pressure under standard conditions, 101.3kPa, Atmospheric pressure at the sampling point during sampling, kPa. p
7.2 Use the calculation factor for drawing the standard curve to calculate the concentration of methyl-1605 in the air according to formula (3): A
Where:
2 × (h-ho) ×Bs
Concentration of methyl-1605 in the air, mg/m3, Average peak height of sample solution, mm,
Average peak height of blank solution, mm
Calculation factor obtained from 6.2.1, μg/(mL·mm), 2 Volume of sample solution, mL
E——Desorption efficiency of silica gel determined by experiment. 7.3 Use the single-point correction method to calculate the concentration of methyl-1605 in the air according to formula (4): 2 (H-HO) × f
Where:
-Concentration of methyl-1605 in the air, mg/m2, h--Average peak height of sample solution, mm,
-Average peak height of blank solution, mm,
f-Correction factor obtained from 6.2.2, μg/(mL·mm). Other symbols are the same as formula (3).
8 Precision and accuracy
(3)
(4)
The recovery rate of the sample with 1 μg standard methyl-1605 was 91~104%, with an average of 98%. The combined coefficient of variation of repeated measurements in the concentration range of 0.2~1.0 μg/mL was less than 10%. 498
A1 Gas chromatography analysis conditions:
Column temperature: 220℃,
Vaporization chamber temperature: 250℃,
Detector temperature: 230℃,
GB 11734—89
Appendix A
Gas chromatography determination conditions and chromatogram of methyl-1605 (reference)
Air flow rate: a.150mL/min, b.80mL/min, hydrogen flow rate: 170mL/min,
Carrier gas (N,) flow rate: 45mL/min.
A2According to the chromatographic conditions of A1, the chromatograms of five organophosphorus pesticides are shown in Figure A1. (5)
(4)
Gas chromatograms of five organophosphorus pesticides
DDVP, 2-dimethoate, 3-methyl-1605, 4-malathion, 5-ethyl-1605A 3 Retention time of organophosphorus pesticides
Organophosphorus pesticides
Methyl-1605
Malathion
Ethyl-1605
Additional remarks:
Retention time
3'8″
5'5”
This standard is proposed by the Health Supervision Department of the Ministry of Health. This standard was drafted by Jiangsu Provincial Health and Epidemic Prevention Station, Suzhou City Health and Epidemic Prevention Station, and Nanjing City Health and Epidemic Prevention Station. The main drafters of this standard are Wu Caigang, Shi Xiaoping, Liu Lianhua, Huang Fuxin, and Wang Xican. This standard is interpreted by the Environmental Health Monitoring Institute of the Chinese Academy of Preventive Medicine, the technical unit entrusted by the Ministry of Health.
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