Determination of total hydrocarbons in ambient air by gas chromatography

1. Scope:

This method is applicable for the determination of total hydrocarbons in the air. The hydrocarbons (C1~C8) measured by the hydrogen flame detector are total hydrocarbons, calculated as methane. This method uses a syringe to collect air samples and directly measures them using a gas chromatograph with a hydrogen flame ionization detector. The sample is introduced into the detector through an empty column or glass bead damping column to determine the total hydrocarbon content. The measurement range of the method varies depending on the instrument used. The lower limit of total hydrocarbon determination is 0.14mg/m3. When measuring the total hydrocarbon content in air using nitrogen as the carrier gas, the total hydrocarbon peak includes oxygen components. Since oxygen in the sample has an effect on the response value, the blank value is obtained by purifying the air with hydrocarbon removal, and the oxygen component value is deducted from the total hydrocarbon peak.

2. Reagent:

2.1 Carrier gas and auxiliary gas

2.1.1 Nitrogen: 99.9% pure nitrogen. Purify with a purification tube containing 5A molecular sieve.

2.1.2 Hydrogen: 99.9%. Purify with a purification tube containing silicone and activated carbon.

2.1.3 Air: supplied by high-pressure steel cylinders or oil-free air compressors, purified with silicone and activated carbon purification tubes.

2.1.4 Purified Air: Processed by a purified air device for hydrocarbon removal (see Appendix A for details).

2.2 Silanized glass microspheres.

2.3 Chromatographic standard: Methane standard gas with nitrogen as the base gas at around 7.1mg/m3 (10ppm).

3. Instrument:

3.1 Instrument: Gas chromatograph equipped with hydrogen flame ionization detector.

3.1.1 Main components of the instrument: equipped with a hydrogen flame ionization detector, column heating furnace, temperature regulator, injection port heater, detector heater and corresponding temperature regulator, amplifier, etc.

3.1.2 Control the pressure gauge, flow meter of the carrier gas, and indicator flow meter of the auxiliary gas.