Some standard content:
National Standard of the People's Republic of China
Health standard for p-nitroaniline in the air of workplaceSubject content and scope of application
GB16242-1996
This standard specifies the maximum permissible concentration of p-nitroaniline in the air of workplace and its monitoring and inspection methods. This standard applies to all types of enterprises that produce and use p-nitroaniline. 2 Hygiene requirements
The maximum permissible concentration of p-nitroaniline in the air of workplace is 3mg/m (skin). 3 Monitoring and inspection methods
The monitoring and inspection methods of this standard adopt ultraviolet spectrophotometry [see Appendix A (supplement) and gas chromatography [see Appendix B supplement).
Approved by the State Administration of Technical Supervision on April 3, 1996, and implemented on September 1, 1996
A1 Principle
GB 16242—1996
Appendix A
Ultraviolet spectrophotometry
(Supplement)
The 95% ethanol solution of p-nitroaniline has an appropriate absorption value at a wavelength of 372nm. Its absorbance and concentration follow Beer's law and can be quantified by ultraviolet spectrophotometry.
A2 Instruments
A2.1 Silica gel sampling tube: Take a glass tube with a length of 120mm and an inner diameter of 4 to 4.5mm, and install two sections of 40 to 60 mesh treated silica gel, 200mg in the front section and 100mg in the back section. The middle and both ends are separated and fixed with absorbent cotton, and the two ends are tightly covered with plastic caps. A2.2 Sampling pump, 0~1.5L/min.
A2.3 Centrifuge.
A2.4 Ground-mouth centrifuge tube with stopper, 5mL.
Ultraviolet spectrophotometer.
A3 ReagentsWww.bzxZ.net
A3.1 Silica gel
Treatment method: Add 1+1 hydrochloric acid to 40-60 mesh silica gel and soak for one day and night, wash with water until there is no nitrogen ion, drain the water, and then rinse with 95% ethanol three times, dry at 90-100℃, activate at 320℃ for 4h, cool and put into tube. A3.2 95% ethanol
A3.3 Standard solution: Accurately weigh 5.0mg of p-nitroaniline, dissolve it in 95% ethanol and dilute to 50mL, prepare a p-nitroaniline solution of 1mL=100μg; then take an appropriate amount of this solution and dilute it to a 1mL-10ug p-nitroaniline standard solution. A4 Sampling
Open the sampling tube at the sampling site and extract 20L of air at a rate of 1.0mL/min. A5 Analysis steps
A5.1 Control experiment: Bring the silicone tube to the site, but do not extract air, and analyze the sample as a blank control. A5.2 Sample processing: Pour the front and rear sections of the silicone tube together with the front absorbent cotton into a stoppered centrifuge tube, add 4mL of 95% ethanol to each, shake well, soak for 30 minutes, and centrifuge. A5.3 Drawing of the standard curve.
Prepare the standard tube according to Table A1.
Use tube 0 as a reference, measure the absorbance at a wavelength of 372nm, and draw a standard curve. Table A1 Preparation of p-nitroaniline standard tube
Standard solution, mL
95% ethanol, mL
p-nitroaniline content, μg
GB 16242-1996
A5.4 Determination: Take the supernatant after centrifugation, take the blank control as reference, measure the absorbance at a wavelength of 372nm, check the p-nitroaniline standard curve, and calculate the p-nitroaniline content.
A6 Calculation
Where: X—concentration of p-nitroaniline in the air, mg/m; content of p-nitroaniline in the silica gel before and after C, ug; V. ---converted to the sampling volume under standard conditions, L. A7 Description
. (Al)
A7.1 The linear range of this method is 0~~40μg/4mL. When the concentration of p-nitroaniline is 10, 20, 30, 40μg/4mL, the relative standard deviation is 2.43%, 2.75%, 2.78% and 6.86% respectively. The detection limit of this method is 0.68μg/4mL.
A7.2 The sampling efficiency of this method is 96.6%, and the desorption efficiency is 97.2%±1.4%. A7.3 Attention points for determination: When taking the sample supernatant, it must be carefully sucked into the cuvette with a pipette, otherwise the result will be high due to the suspension of small silica gel particles.
A7.4 In order to collect p-nitroaniline in both vapor and aerosol states at the same time, the sampling speed is limited to 1.0~~1.5L/min. The silica gel sampling tube after sampling is stored in a desiccator at room temperature and can be stable for at least one week. A7.5 Coexisting substances in the workshop air: aniline, dimethylaniline, and p-nitrofluorobenzene have no interference with this determination. Appendix B
Gas chromatography
(Supplement)
B1 Principle
Use a silica gel sampling tube to collect p-nitroaniline in the air, desorb it with ethanol, separate it with an OV-17 column, and detect it with a hydrogen flame ionization detector. The retention time is used for qualitative analysis and the height is used for quantitative analysis. B2 Instruments
B2.1 Silicone tube: Use a glass tube with a length of 120mm and an inner diameter of 4 to 4.5mm, and install two sections of 40 to 60 mesh treated silica gel. The front section is filled with 200 mg, and the rear section is filled with 100 mg. The middle and both ends are separated and fixed with glass wool. After installation, use plastic caps to cover both ends for use. B2.2 Sampling pump, 0 to 1.0L/min.
B2.3 Micro syringe, 10μL.
B2.4 Ground-mouth centrifuge tube with stopper, 5mL. B2.5 Gas chromatograph, hydrogen flame ionization detector, 10 ng of p-nitroaniline gives a signal-to-noise ratio of at least 3:1. Chromatographic column: 1.6m long, 4mm inner diameter, glass column. OV-17: ChromosorbW AW-DMCS=2:10; Column temperature: program heating 80～210℃ (stop at 80℃ for 4min, then heat to 210℃ at 8℃/min and stop for 4min); Detection chamber temperature: 250℃;
Vaporization chamber temperature: 250℃;
Carrier gas (nitrogen): 30mL/min.
B3 Reagents
GB16242--1996
B3.1 Silica gel, 40～60 mesh, should be activated before loading. Treatment method: Inject silica gel into 1+1 hydrochloric acid and soak for a day and night, then wash with water until there is no chloride ion, dry silica gel at 90-100℃, activate at 320℃ for 4h, cool and put into tube. B3.2 Glass wool.
B3.3 95% (V/V) ethanol, redistilled.
B3.4 OV-17, chromatographic stationary liquid.
B3.5 Chromosorb WAW-DMCS chromatographic support, 60~~80 mesh. B3.6 Standard solution: Accurately weigh 0.200g p-nitroaniline, dissolve it in 95% ethanol in a 25mL volumetric flask, add 95% ethanol to the mark, and shake well. This solution is a standard stock solution of 1mL-8000μg, dilute to the required concentration before use. B4 Sampling
Open the silicone tube at the sampling site, connect the 100mg end to the sampler and place it vertically, collect 5L of air at a rate of 0.5L/min, put plastic caps on both ends of the tube after sampling, and analyze as soon as possible. B5 Analysis steps
B5.1 Control experiment: Same as sampling, bring the silicone tube to the site, but do not extract air, and analyze the sample as a blank control. B5.2 Sample processing: Take out the glass wool in front of the silicone sampling tube, pour the silicone and the rear section of the silicone into 5mL centrifuge tubes respectively, then add 1ml95% ethanol (3.3) to soak, let it soak for 30min, and stir with a glass rod before analysis. B5.3 Drawing of standard curve: Take a certain amount of p-nitroaniline standard stock solution and dilute it with ethanol (3.3) to prepare 1530 and 150 μg/mL standard solutions. Take 2uL of each solution for injection, measure retention time and peak height, repeat 3 times for each concentration, take the average of peak height, plot p-nitroaniline content against peak height, draw standard curve, and use retention time as qualitative indicator. B5.4 Sample analysis: Take 2μL of sample solution desorbed with ethanol for injection, use retention time for qualitative analysis and peak height for quantitative analysis. The chromatogram of p-nitroaniline is shown in Figure B1.
p-Sphingylaniline
812162024
Time, min
Figure B1 Chromatogram of p-nitroaniline
B6 Calculation
GB16242-1996
B6.1 Convert the volume of the sample into the volume under standard conditions according to formula (1). 273
V. = V×
Wherein: V. — Sample volume under standard conditions, L; — Sample volume, L;
t Temperature, °C;
p Atmospheric pressure, kPa.
B6.2 Calculate the concentration of p-nitroaniline in the air according to formula (2). Ci+C2
Wherein: X-
-concentration of p-nitroaniline in the air, mg/m\; force
-are the contents of the front and rear silica gel extracts, g, C, C2
V. —-sample volume under standard conditions, L. B7 Description
(B1)
(B2)
B7.1The detection limit of this method is 1×10-2μg (injection of 2μL liquid sample). The response signal of p-nitroaniline with a sensitivity of 10ng is greater than 3 times the baseline noise. Under the experimental conditions of this method, the determination range of p-nitroaniline is 5.0～~200μg/mL. The relative standard deviations of p-nitroaniline at 16, 32, and 160μg/mL are 1.2%, 1.6%, and 1.3%, respectively. B7.2 The average penetration capacity of this method is 22.2 mg, and the sampling efficiency is 100%. B7.3 After the silica gel tube collects p-nitroaniline, the two ends of the tube are tightly covered with plastic caps. At room temperature, it can be stored for at least 7 days. B7.4 Since ethanol and silica gel batch number have an effect on the desorption efficiency of p-nitroaniline, the desorption efficiency should be measured in each laboratory. Under the experimental conditions of this method, the desorption efficiency of 16, 32, and 64 μg p-nitroaniline is 102.4%, 92.7%, and 94.3%, respectively, and the total average desorption efficiency is 96.5%.
B7.5 The silica gel sampling tube can collect other aromatic amines that coexist with p-nitroaniline, such as aniline, toluidine, and xylidine. Under the chromatographic conditions, due to different retention times, they do not interfere with the determination of p-nitroaniline. Additional notes:
This standard is proposed by the Ministry of Health of the People's Republic of China. This standard was drafted by Tianjin Institute of Labor Hygiene and Occupational Diseases and Zhejiang Institute of Labor Hygiene and Occupational Diseases Prevention and Control. The main drafters of this standard are Xu Jia, Yuan Xuehong, Li Zhihua and Yue Junyi. The Institute of Labor Hygiene and Occupational Diseases of the Chinese Academy of Preventive Medicine, the technical unit entrusted by the Ministry of Health, is responsible for the interpretation of this standard.
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