What is the principle of gas chromatography?

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Briefly describe the principle and application of top gas chromatography

GC vials

Headspace gas chromatography (HS-9) is a chromatographic technique that adds a headspace sampler in front of the gas chromatograph inlet, often interpreted as an instrument that combines a headspace sampler with a gas chromatograph. It uses the sample to be tested (gas-liquid and gas-solid) to equilibrate and then take its volatile gas portion into the gas chromatograph. It is specially designed for the analysis of volatile trace components, such as many volatile organic solvents such as methanol and ethanol; floral aromas and perfumes in different seasons, Chinese herbal medicines with volatile components, vegetables and condiments with special odors, etc. It can be used for quantitative analysis. Headspace gas chromatography coupled with mass spectrometry is used for qualitative analysis of unknown volatile components.
Headspace gas chromatography is often used for qualitative and quantitative confirmation and analysis of alcohol in the blood of drivers or pedestrians after a traffic accident, standard analysis of residual solvents before and after Chinese and Western medicines are put on the market, and toxic gases and volatile poisons in criminal cases. Identification, etc., and many other industries need to control the quality of products or develop new products. This method of analysis avoids the problem of overloading and contamination of the analytical column by moisture, high boilers or non-volatile materials. Moreover, the operation is simple and fast, and the analysis result is as sensitive, reliable and accurate as the gas chromatogram.

Precautions
1. Since the carrier gas entering the headspace enters the GC at the same time, the gas used for the headspace should also be purified.2. The headspace bottle heating temperature, the metering tube temperature, the transmission line temperature should be small to large, and the transmission line is less than or equal to the inlet port temperature.3. When applying headspace, the total flow of GC gas should be the headspace airflow plus the GC gas flow. Care should be taken when calculating the split ratio. It can be calculated after measuring with a flow meter.4. In the time setting, the time for filling the sample tube should be sufficient, the balance time of the quantitative tube should not be too long, and the injection time should be long enough.5. If the pressure adjustment of the headspace sampler is manual, the sample pressurization and carrier gas pressure values ??should be recorded after the method is built to avoid pressure changes due to changes in valve status.

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