GBZ/T 300.68-2017Determination of toxic substances in workplace air - Part 68: Styrene, methylstyrene and divinyl benzene (English PDF)

4.3 Reagents

4.3.1 Carbon disulfide. No interfering peaks are found in chromatographic identification.

4.3.2 Standard solution. Add carbon disulfide to a volumetric flask, weigh it accurately, then add a certain amount of styrene and/or methyl styrene, weigh it accurately again, and make up the volume with carbon disulfide. Calculate the concentration of the solution from the difference in weight, which is the styrene and/or methyl styrene standard solution. Or prepare it with a nationally recognized standard solution.

4.4 Sample collection, transportation and storage

4.4.1 On-site sampling shall be carried out in accordance with GBZ 159.

4.4.2 Short-time sampling. At the sampling point, use an activated carbon tube to collect air samples at a flow rate of 100 mL/min for 15 minutes.

4.4.3 Long-term sampling. At the sampling point, use an activated carbon tube to collect air samples at a flow rate of 50 mL/min for 2~8 hours.

4.4.4 After sampling, immediately seal both ends of the activated carbon tube and place it in a clean container for transportation and storage. The sample can be stored in a refrigerator for 14 days.

4.4.5 Sample blank. At the sampling point, open both ends of the activated carbon tube and seal them immediately, then transport, store and measure together with the sample.

Each batch of samples shall have no less than 2 sample blanks.

4.5 Analysis steps

4.5.1 Sample treatment. Place the front and rear section activated carbon into two

solvent desorption bottles respectively, add 1.0 mL of carbon disulfide to each, seal, and desorb for 30 minutes, shaking occasionally. The sample solution is for determination.

4.6.3 The time-weighted average exposure concentration (CTWA) in the air shall be calculated in accordance with the provisions of GBZ 159.

4.7 Description

4.7.1 This method is developed in accordance with the method and requirements of

GBZ/T 210.4.The detection limit of this method is 2.5 µg/mL, the lower limit of quantification is 8.3 µg/mL, and the quantitative determination range is 8.3 µg/mL~900

µg/mL; based on the collection of 1.5 L air sample, the minimum detection concentration is 1.7 mg/m3, and the minimum quantitative concentration is 5.5 mg/m3;

the relative standard deviation is 4.2%~5.3%, the penetration capacity (100 mg of activated carbon) is 6.9 mg, and the desorption efficiency is 79.5%. The desorption efficiency of each batch of activated carbon tubes shall be measured.

4.7.2 This method can also be used with other equivalent gas chromatographic columns.

Constant temperature measurement or programmed temperature measurement can be selected according to the measurement requirements.

5.1 Principle

The vaporous styrene in the air is collected by activated carbon, injected after thermal desorption, separated by a gas chromatography column, and detected by a hydrogen flame ionization detector. The retention time is used for qualitative analysis and the peak height or peak area is used for quantitative analysis.

5.2 Instruments

5.2.1 Activated carbon tube. thermal desorption type, containing 100 mg of activated

carbon.

5.2.2 Air sampler. with a flow range of 0 mL/min ~ 500 mL/min.

5.2.3 Thermal desorber.

5.2.4 Syringe. 1 mL, 100 mL.

5.2.5 Gas chromatograph with a hydrogen flame ionization detector. Reference

operating conditions.

a) Chromatographic column. 30 m×0.32 mm×0.5 µm, FFAP;

b) Column temperature. 80 °C;

c) Vaporization chamber temperature. 150 °C;

d) Testing room temperature. 150 °C;

e) Carrier gas (nitrogen) flow rate. 1 mL/min;

f) Split ratio. 10.1.

5.3 Reagents

5.3.1 Styrene. At 20 °C, the mass of 1.0 µL of gas is 0.9060 mg.

5.3.2 Standard gas. Use a microsyringe to accurately extract 1.0 µL of styrene, inject it into a 100 mL airtight glass syringe, dilute it to 100.0 mL with clean air, and prepare

9.06 µg/mL standard gas. Or use a nationally recognized standard gas to prepare.

5.4 Sample collection, transportation and storage

5.4.1 On-site sampling shall be carried out in accordance with GBZ 159.

5.4.2 Short-time sampling. At the sampling point, use an activated carbon tube to collect air samples at a flow rate of 100 mL/min for 15 minutes.

5.4.3 Long-term sampling. At the sampling point, use an activated carbon tube to collect air samples at a flow rate of 50 mL/min for 2~8 hours.

5.4.4 After sampling, immediately seal both ends of the activated carbon tube and place it in a clean container for transportation and storage. The sample can be stored in a refrigerator for 14 days.

5.4.5 Sample blank. At the sampling point, open both ends of the activated carbon tube and seal them immediately, then transport, store and measure together with the sample.

Each batch of samples shall have no less than 2 sample blanks.

5.5 Analysis steps

5.5.1 Sample treatment. Place the activated carbon tube in a thermal desorber, connect

the gas inlet to a 100 mL syringe and the other end to a carrier gas (nitrogen), and desorb to 100.0 mL at 350 °C at a flow rate of 50 mL/min. The sample gas is used for determination.

5.5.2 Preparation of the standard curve. Take 4~7 100 mL airtight glass syringes, inject

0.0 mL~10.0 mL of standard gas respectively, dilute with clean air to 100.0 mL, and form a styrene standard series with a concentration range of 0.0 µg/mL~0.91 µg/mL.

Referring to the instrument operating conditions, adjust the gas chromatograph to the optimal measurement state, inject 0.50 mL, and measure the peak height or peak area of each concentration in the standard series. Draw a standard curve or calculate a regression equation based on the measured peak heights or peak areas vs. the corresponding styrene concentrations (µg/mL), and the correlation coefficient shall be

5.7.2 This method can also be used with other equivalent gas chromatographic columns.

Constant temperature measurement or programmed temperature measurement can be selected according to the measurement requirements.

5.7.3 Styrene is easily adsorbed on the syringe wall and easily polymerized. The sample shall be measured as soon as possible after desorption.

5.7.4 If the concentration of the analyte in the workplace air is high and penetration may occur, two thermal desorption-activated carbon tubes shall be connected in series for sampling.

6.1 Principle

Vaporous divinylbenzene in the air is collected by activated carbon, desorbed by acetone-carbon disulfide solution and then injected, separated by a gas chromatography column and detected by a hydrogen flame ionization detector. The retention time is used for qualitative analysis and the peak height or peak area is used for quantitative analysis.

6.2 Instruments

6.2.1 Activated carbon tube. solvent desorption type, containing 100 mg/50 mg of

activated carbon.

6.2.2 Air sampler. with a flow range of 0 mL/min ~ 500 mL/min.

6.2.3 Solvent desorption bottle. 5 mL.

6.2.4 Microsyringe. 10 µL.

6.2.5 Gas chromatograph with a hydrogen flame ionization detector. Reference

operating conditions.

a) Chromatographic column. 30 m×0.32 mm×0.25 µm, 5% phenylmethylsiloxane;

b) Column temperature. the initial temperature is 100°C; rise to 150 °C at

10 °C/min, and maintain for 3 min;

c) Vaporization chamber temperature. 200 °C;

d) Testing room temperature. 200 °C;

e) Carrier gas (nitrogen) flow rate. 1 mL/min;

f) Split ratio. 10.1.

6.3 Reagents

6.3.1 Desorption solution (acetone-carbon disulfide solution). Dilute 30 mL of acetone

to 100 mL with carbon disulfide. Chromatographic identification shows no interfering peaks.

6.3.2 Standard solution. Add desorption solution to a volumetric flask, weigh accurately, then add a certain amount of divinylbenzene, weigh accurately again, and adjust the volume with the desorption solution. Calculate the concentration of the solution from the difference between the two weighings, which is the standard stock solution and can be stored in a refrigerator at 4 °C for 3 days. Before use, dilute with desorption solution to a 2400.0 µg/mL divinylbenzene standard solution. Or prepare it with a nationally recognized standard solution.

6.4 Sample collection, transportation and storage

6.4.1 On-site sampling shall be carried out in accordance with GBZ 159.

6.4.2 Short-time sampling. At the sampling point, use an activated carbon tube to collect air samples at a flow rate of 200 mL/min for 15 min.

6.4.3 Long-term sampling. At the sampling point, use an activated carbon tube to collect air samples at a flow rate of 50 mL/min for 2~8 hours.

6.4.4 After sampling, immediately seal both ends of the activated carbon tube and place it in a clean container for transportation and storage. The sample can be stored at room temperature for 7 days.

6.4.5 Sample blank. At the sampling point, open both ends of the activated carbon tube and seal them immediately, then transport, store and measure together with the sample.

Each batch of samples shall have no less than 2 sample blanks.

6.5 Analysis steps

6.5.1 Sample treatment. Place the front and rear section activated carbon into two

solvent desorption bottles respectively, add 1.0 mL of desorption solution to each bottle, seal it, desorb for 30 min, and shake it occasionally. The sample solution is for determination.

6.5.2 Preparation of the standard curve. Take 4~7 volumetric flasks and dilute the

standard solution with desorption solution to form a divinylbenzene standard series with a concentration range of 0.0 µg/mL~2400.0 µg/mL. Referring to the instrument operating conditions, adjust the gas chromatograph to the optimal measurement state, inject 1.0 µL, and measure the peak height or peak area of each concentration in the

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