WS/T 141-1999 Gas chromatography method for determination of total non-methane hydrocarbons in workplace air
Some standard content:
Health Industry Standard of the People's Republic of China
WS/T 141--1999
Gas Chromatographic Determination of Total Hydrocarbon Except for Methane-Gas Chromatographic Method
Workplace air-Determination of total hydrocarbon except for methane-Gas chromatographic method1999-12-29 Issued
Issued by the Ministry of Health of the People's Republic of China
Implemented on 2000-05-01
WS/T141—1999
This standard is a monitoring method that matches the labor hygiene standard and is used to monitor the concentration of non-methane total hydrocarbons in the workplace air. This standard is proposed after laboratory research and field verification with reference to foreign monitoring methods and in combination with my country's situation. This standard will be implemented from May 1, 2000. This standard was proposed by the Ministry of Health of the People's Republic of China. Drafting units of this standard: Jiangsu Provincial Health and Epidemic Prevention Station, Nanjing Municipal Health and Epidemic Prevention Station. The main drafters of this standard are: Wang Xican, Sheng Juanfen, Tang Shigui, Xiao Shangjia. The Ministry of Health entrusted the Institute of Labor Health and Occupational Diseases of the Chinese Academy of Preventive Medicine to interpret this standard. 1 Scope
Health Industry Standard of the People's Republic of China
Gas chromatographic determination method of non-methane total hydrocarbons in workplace air
Workplace air-Determination of total hydrocarbon exceptformethane-Gas chromatographic method This standard specifies the gas chromatographic determination method of non-methane total hydrocarbon concentration in workplace air. This standard is applicable to the determination of non-methane total hydrocarbon concentration in workplace air. 2 Principle
WS/T141-1999
Non-methane total hydrocarbons in the air are collected by activated carbon tubes, injected after thermal desorption, separated by glass microsphere columns, and detected by hydrogen flame ionization detector. Qualitative analysis is based on retention time, and quantitative analysis is based on peak height or peak area. 3 Instruments
3.1 Activated carbon tube: Use a glass tube with a length of 150mm, an inner diameter of 4mm, and an outer diameter of about 6mm, and load it with 100mg 20~40 mesh shell activated carbon. Before loading the tube, treat the activated carbon with nitrogen at 300350℃ for 4h. Fix the two ends with a small amount of glass wool. After loading the tube, blow nitrogen at 350℃ for 5~10min, seal the two ends of the glass tube, and put on a plastic cap for standby. 3.2 Gas sampler: flow rate 0~2L/min. 3.3 Syringe: 100mL10mL, 1.0mL. 3.4 Micro syringe: 10μL.
3.5 Thermal desorber, the thermal desorber is mainly composed of a heater, a temperature controller, a temperature gauge and a gas flow controller. The temperature control range is 100~400℃. The flow control range is 50~100mL/min. 3.6 Temperature box: 20℃~60℃, ±1℃.
3.7 Gas chromatograph: hydrogen flame ionization detector. The signal-to-noise ratio given by 0.3ng n-hexane is not less than 3:1. Chromatographic column: column length 2m, inner diameter 4mm, glass column or stainless steel column; glass microsphere stationary phase: 60~80 mesh;
Column temperature: 110℃;
Detection chamber temperature: 160℃;
Vaporization chamber temperature: 160℃,
Carrier gas (nitrogen): flow rate 35mL/min. 4 Reagents
The experimental water is distilled water.
4.1 Glass microsphere stationary phase: 60~80 mesh. 4.2 n-hexane (chromatographic grade).
Approved by the Ministry of Health of the People's Republic of China on December 29, 1999, and implemented on May 1, 2000
5 Sampling
WS/T 141-—1999
Saw the activated carbon tube at the sampling site, with the aperture of at least 2mm at both ends, and the sawn edge should be flat and placed vertically. Collect 3 to 6L of air at a flow rate of 0.3L/min. After sampling, put plastic caps on both ends of the tube, mark the sampling air inlet end, and bring it back to the laboratory for analysis. The analysis should be completed within two weeks.
6 Analysis steps
6.1 Control test: Bring an activated carbon tube that has not been sampled to the sampling point. Except for not collecting air, the rest of the operations are the same as the sample, as a blank control for the sample.
6.2 Sample processing: Remove the plastic caps at both ends of the sample tube, place it in a thermal desorber, so that its sampling air inlet end is the thermal desorption outlet end, and connect a 100mL syringe to the outside. After preheating for 30 seconds, desorb to 100 mL at 350 ° C with nitrogen at a flow rate of 50 mL/min, and place in a 35-40 ° C incubator for analysis.
6.3 Drawing of standard curve: Use a micro-syringe to accurately extract a certain amount of n-hexane (the mass of 1 μL n-hexane at 20 ° C is 0.659 mg), inject it into a syringe with 100 mL gas, and mix it. Place it in a 35-40 ° C incubator to prepare a standard gas of a certain concentration. Take another 3 100 mL syringes and dilute them with clean air to a standard series containing 0.05.0.20, 1.00 μg/mL. Adjust the instrument to the optimal state according to the operating conditions, inject 1.0 mL, measure the retention time and peak height (or peak area), measure the standard series separately, measure each concentration 3 times, and calculate the average of the peak height (or peak area). Use the average of the peak height (or peak area) as the ordinate and the concentration of n-hexane (ug/mL) as the abscissa to draw a standard curve. Retention time is used as a qualitative indicator. 6.4 Determination: Under the same conditions as the standard series determination, the sample and blank control are measured separately, 1.0 mL of sample desorption gas is injected, and the retention time is used for qualitative analysis. After subtracting the peak height of the blank control from the measured sample peak height, the concentration of non-methane total hydrocarbons (μg/mL) is obtained from the standard curve. 7 CalculationbZxz.net
7.1 Convert the volume of the collected air into the volume under standard conditions according to formula (1). 273
Vo=V×273+×
Where: V. ———Sampling volume converted to standard conditions, LV—Sampling volume, L
p——Atmospheric pressure of the sampling site, kPa; —Air temperature of the sampling site, ℃.
7.2 Calculate the concentration of non-methane total hydrocarbons in the air according to formula (2). CcX100
Where: C-concentration of non-methane total hydrocarbons in air, mg/mc-concentration of non-methane total hydrocarbons obtained from the standard curve, ug/mL100-total volume of sample desorption gas, mL; V. Converted to the sampling volume under standard conditions, L. 8 Explanation
(2)
8.1 The detection limit of this method is 1×10-μg/mL, the minimum detection concentration is 0.01mg/m (sampling volume is 3L, thermal desorption volume is 100mL), and the linear range is 0.005~3μg/mL. When the concentration of non-methane total hydrocarbons is 0.05, 0.20 and 1.00μg/mL, the relative standard deviation of this method is 4.45%, 4.39% and 3.60% respectively. 2
WS/T1411999
8.2 The average sampling efficiency of this method is 97.5% (the concentration of non-methane total hydrocarbons in the air is 200~2000mg/m2); the penetration capacity is 13.5mg (relative humidity is 90%), and the average desorption efficiency is 99.7%. 8.3 Stability of sample storage: The samples in the carbon tube can be stable for more than 14 days at room temperature. 8.4 The standard series gas and the desorbed samples should be analyzed in a thermostat to prevent the vaporized samples from condensing and adsorbing in the syringe, reducing the concentration and affecting the repeatability.
8.5 Interference factors: Under the chromatographic conditions, the retention time of non-methane total hydrocarbons is 0.49~0.50min, and the retention times of ethanol, acetone, and ethyl acetate under the same chromatographic conditions are 0.72min, 0.85min0.90min, respectively, which do not interfere with the determination of non-methane total hydrocarbons. Health Industry Standard of the People's Republic of China Gas Chromatographic Determination of Non-methane Total Hydrocarbons in Air of Workplaces WS/T141-1999 Published by China Standards Press No. 16, Sanlihebei Street, Fuxingmenwai, Beijing Postal Code: 100045 Tel: 68522112 China Standards Zhun Press, Zahuangdao Printing Factory, Xinhua Bookstore, Beijing Distribution Office, Xinhua Bookstores, all over the country, exclusive copyright, no reproduction allowed
Format 880×12301/16
Printing sheet 1/2 Number of words 6,000 words
First edition September 2000 First printing September 2000 Number of copies 1-800
Book number: 155066·2-13196
Heading 418-45
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.