Some standard content:
National Standard of the People's Republic of China
Health standard for tetrahydrofuran in the air of workplace
Health standard for tetrahydrofuran in the air of workplace1 Subject content and scope of application
This standard specifies the maximum allowable concentration of tetrahydrofuran in workplace air and its monitoring and inspection methods. This standard applies to all types of enterprises that produce and use tetrahydrofuran. 2 Hygiene requirements
The maximum allowable concentration of tetrahydrofuran in workplace air is 300mg/m3. 3 Monitoring and inspection methods
GB 16231—1996
The monitoring and inspection methods of this standard adopt gas chromatography, see Appendix A (supplement) and Appendix B (supplement). Approved by the State Administration of Technical Supervision on April 3, 1996 530
Implemented on September 1, 1996
A1 Principle
GB16231-1996
Appendix A
Gas chromatography
(Supplement)
Tetrahydrofuran in the air is adsorbed in a 401 organic carrier sampling tube at room temperature, desorbed by carbon disulfide, separated by a di-phthalate column, detected by a hydrogen flame ionization detector, qualitative by retention time, quantitative by height. A2 Instrument
A2.1 Sampling tube: A hard glass tube with an inner diameter of 4.5 mm and a length of 120 mm. 150 mg and 75 mg of the treated 401 organic carrier are loaded into the front and back sections, the middle and lower ends are separated and fixed by polyurethane foam plastics, the upper end is plugged with glass wool, and after loading, a rubber cap is put on and placed in a dryer for use.
A2.2 Rubber cap: 60mL vial stopper.
A2.3 Syringe: 2ml.
A2.4 Microsyringe: 10μL.
A2.5 Test tube with stopper: 10ml.
A2.6 Gas chromatograph, hydrogen flame ionization detector. Chromatographic column: 2m long, 3mm inner diameter, stainless steel column; stationary liquid: di-orthophthalate: acid-washed white 102 support-20:100; column temperature: 95℃;
Detection room temperature: 145℃,
Carrier gas (nitrogen): 25mL/min;
A3 Reagents
A3.1 Di-orthophthalate, chromatographic stationary liquid. A3.2 Acid-washed white 102 support, 60~80 mesh. A3.3401 Organic carrier, 20-40 mesh, soak and shake the carrier with ether, filter out the ether, remove the organic matter adsorbed by the carrier; then wash with methanol to remove the residual ether, then wash the methanol with water, put it in a porcelain plate, and dry it at 102℃ for 2h. A3.4 Methylhydrogen sulfonate (chemically pure).
A3.5 Carbon disulfide (analytical pure): It should be free of impurities after chromatographic analysis. If there is, it should be placed in a separatory funnel and extracted with 5%-10% polyoxymethylene sulfuric acid solution until the extract is colorless, then washed with water until neutral, dehydrated with anhydrous sodium sulfate, and after chromatographic identification, there is no impurity peak and then placed in the refrigerator for use.
A3.6 Preparation of polyoxymethylene: Pour 200mL of concentrated sulfuric acid into 300mL of formaldehyde solution (approximate proportion), spread evenly, let it stand for several days, and flocculent precipitation will be produced. Filter the precipitate to obtain white solid polyoxymethylene. A3.7 Standard solution: Use carbon disulfide as solvent to prepare standard solutions containing 0.005, 0.025, 0.050, 0.100, and 0.250 μg/μL of tetrahydrofuran.
A4 Sampling
Open the sampling tube at the sampling point, connect the 75mg end to the sampling pump, and place it vertically. Sampling at a speed of 0.14L/min. After sampling, pour the front and rear sections of the carrier into the stoppered graduated test tube as soon as possible. The tube mouths are sealed with three layers of polyester film and tightly covered with rubber caps. Place in the refrigerator and store for 7 days.
A5 Analysis steps
GB 16231—1996
A5.1 Control test: Bring the sampling tube to the site and operate with the same sample as the blank control except that no air sample is collected. A5.2 Sample analysis: Add 2mL and 1mL of carbon disulfide to the front support and the back support respectively, shake for 1min, and place for 0.5h, then take 2μL of the lower carbon disulfide solution for sampling, and make a standard sample at the same time, use retention time for qualitative analysis and peak height for quantitative analysis. When analyzing the samples, there should be a control (blank) tube for comparison. www.bzxz.net
A5.3 Standard curve drawing: Take 2μL of different contents of tetrahydrofuran standard solution (A3.7), directly perform chromatographic analysis, measure its retention time and peak height, measure each concentration 3 times, take the average of the peak height, plot the tetrahydrofuran content against the peak height, and draw a standard curve. A6 Calculation
1.×desorption volume (m)7+「A,×
desorption volume (mL)
injection volume (μL)」
injection volume (μL)
where: C—tetrahydrofuran concentration in air, mg/m\; A, A2——tetrahydrofuran content in the front and rear eluents of the 401 organic carrier sampling tube, μg; V. ——converted to the sampling volume under standard conditions, L. A7 Explanation
A7.1 The detection limit of this method is 0.0051μg/μL tetrahydrofuran, and the corresponding height is 5mm. A7.2 At a tetrahydrofuran nozzle of 135mg/m2, sampling at a speed of 0.14L/min, the sampling time should be within 19min. A7.3 Toluene, chlorobenzene, furfural and furan that may coexist in the on-site air have no interference with the determination. Appendix B
Gas chromatography
(Supplement)
B1 Principle
Use activated carbon tube to collect tetrahydrofuran in the air, heat and desorb it into a large syringe, separate it with FFAP column, and detect it with hydrogen flame ionization detector. The retention time is used for qualitative analysis and the peak height is used for quantitative analysis. B2 Instrument
B2.1 Activated carbon tube: Use a glass tube with a length of 250mm, an inner diameter of 3.5~4mm, and an outer diameter of about 6mm, and fill it with 100mg 20~40 mesh coconut shell activated carbon. Fix the two ends with a small amount of glass wool. After the tube is installed, blow it with nitrogen at 300~350℃ for 5~10min. When used for a short time, put plastic caps on both ends for storage; when used for a long time, seal the two ends with fire for storage. B2.2 Syringe: 100mL, 1mL.
B2.3 Thermal desorption device: temperature control range is 100～350℃, desorption gas is nitrogen, flow control range is 50～100mL/min. B2.4 Gas chromatograph, hydrogen flame ionization detector. The signal-to-noise ratio given by 2.3ng tetrahydrofuran is not less than 31. Chromatographic column: column length 2m, inner diameter 2mm, glass column, FFAP:Chromosorb WHP carrier = 10:100; column temperature: 55℃;
vaporization chamber temperature: 140℃;
detection chamber temperature: 150℃
carrier gas (nitrogen): 25ml./min.
B3 Reagents
B3.1 Tetrahydrofuran, chromatographic grade.
B3.2FFAP, chromatographic stationary liquid.
GB16231—1996
B3.3Chromosorb WHP carrier, 100~~120 mesh. B4Sampling
Open the activated carbon tube at the sampling site and place it vertically. Use a 100mL syringe to extract 0.21. of air at a rate of 0.1L/min. After sampling, put plastic caps on both ends of the tube and bring it back to the laboratory for analysis. B5Analysis steps
B5.1Control test: Use the activated carbon tube that has not been sampled (the number is 1/10 of the total number of samples, at least 1 tube) according to the sample processing operation as a blank control.
B5.2Sample processing: Remove the plastic caps at both ends of the sample tube, connect it to a 100mL syringe, place it on a thermal desorption device, and desorb it to 100ml at a rate of 1ml/s at 250℃ with nitrogen. B5.3 Drawing of standard curve: Take a certain amount of tetrahydrofuran (the mass of 1uL tetrahydrofuran at 20℃ is 0.8892mg) with a micro syringe and inject it into a 100mL syringe, dilute it with clean air to make a standard gas of a certain concentration, take a certain amount of the above standard gas and dilute it with clean air to make 0.15, 0.60, and 1.5μg/mL tetrahydrofuran standard gas. Take 1mL of each sample, measure the retention time and peak height, repeat 3 times for each concentration, take the average value of the peak height, plot the tetrahydrofuran content against the peak height, and draw a standard curve. The retention time is a qualitative indicator.
B5.4 Determination: Take 1mL of desorbed gas for injection, use the retention time for qualitative analysis and the peak height for quantitative analysis. B6 Calculate
XV.
Where: X-the concentration of tetrahydrofuran in air, mg/m, C-the content of tetrahydrofuran in the desorbed gas found on the standard curve, μgV. - Sample volume under standard conditions, L. B7 Description
B7.1 The detection limit of this method for tetrahydrofuran is 2.3×10-3μg (intake 1.0mL air sample). When the concentration of tetrahydrofuran standard gas is 0.15, 0.60, and 1.5g/mL, the coefficient of variation of the standard gas is 1.1%, 0.9%, and 1.5%, respectively, and the coefficient of variation of the desorbed gas is 1.3%, 1.7%, and 1.7%, respectively.
B7.2 When the concentration of tetrahydrofuran is 5-223mg/m2 and the relative humidity is 57%, the sampling efficiency is 100%. B7.3 Dynamically generate 150~1500mg/m tetrahydrofuran standard gas with humidity of 51% (dry gas) and 89% (wet gas). Collect 200mL tetrahydrofuran standard gas with activated carbon tube; desorb on the same day and after storage for a period of time. The desorption efficiency is 98.2% for dry gas and 97.4% for wet gas. There is little change after storage at room temperature for 1 week. B7.4 GH-1 activated carbon produced by Beijing Guanghua Wood Factory is suitable for the requirements of tetrahydrofuran sampling and thermal desorption, and its penetration capacity is 9.36 mg.
B7.5 When the desorption temperature is 200℃, the desorption efficiency of tetrahydrofuran is greater than 92%. At 300℃, the desorption efficiency does not increase much, while the influence of impurities increases significantly, so the desorption temperature is selected to be 250℃. B7.6 Methanol, ethanol, acetone, isopropanol and n-butanol that may coexist in the on-site air have no interference with the determination. 533
Additional notes:
GB16231-1996
This standard was proposed by the Ministry of Health of the People's Republic of China. This standard was drafted by the Shanghai Institute of Labor Hygiene and Occupational Disease Prevention and Control. The main drafters of this standard are Fu Weizu, Yu Yongdan and Zhang Ge. This standard is interpreted by the Institute of Labor Hygiene and Occupational Diseases of the Chinese Academy of Preventive Medicine, which is the technical management unit entrusted by the Ministry of Health. 534
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