How does Gas Chromatography Work

Chromatography is the process of separating a mixture into its core components for analysis or reuse. Gas chromatography uses an inert gas as a carrying mechanism within that separation, with samples introduced to the gas and then filtered through a solid distillation column.

Key to the process is the retardation (slowing) of the mixture’s elements in the column, which is achieved by filling the latter with a finely divided inert solid coated with a thin layer of reactive liquid or polymer. The stream of gas passes the coated solid and, while the inert gas – by its very nature – won’t react with it, the additional elements it is carrying will.

Each component doesn’t react with the solid simultaneously, however. This means the sample breaks down over time, with each element leaving the column at a certain point depending on its composition. As such, a mixture of various substances can be split into its constituent parts, allowing each to be quantified, studied and/or filtered.

Gas chromatography step-by-step

1. Inert – A stream of inert gas – eg helium or argon – is pumped through the machine in a constant flow as a carrying mechanism.

2. Sample – The sample – blood, for instance – is vaporized and introduced to the gas stream, which transports it into the chromatography separating column.

3. Column – The column is filled with a finely divided inert solid coated with a layer of liquid or polymer to react with individual elements in the sample.

4. Interaction – The various components of the vaporized sample interact at different speeds with the polymer/ liquid-coated solid, slowing and separating them one by one.

5. Detector – As each component of the sample is slowed in the column at different speeds, they pass through the machine’s detector independently, allowing each substance to be measured and filtered.