The 'headspace' is the gas space in a chromatography vial above the sample. Headspace analysis is therefore the analysis of the components present in that gas.
Headspace GC is used for the analysis of volatiles and semi-volatile organics in solid, liquid and gas samples. The popularity of this technique has grown over recent years and has now gained worldwide acceptance for analyses of alcohols in blood and residual solvents in pharmaceutical products.
Other common applications include industrial analyses of monomers in polymers and plastic, flavour compounds in beverages and food products, and fragrances in perfumes and cosmetics.
It is most suited for the analysis of the very light volatiles in samples that can be efficiently partitioned into the headspace gas volume from the liquid or solid matrix sample. Higher boiling volatiles and semi-volatiles are not detectable with this technique due to their low partition in the gas headspace volume. Partitioning is covered in more detail later in this article.
Headspace analysis also lends itself to automation for quality control or sample screening. This is made possible by modern instrumentation being able to reproducibly prepare samples in an efficient manner.
Complex sample matrices, which would otherwise require sample extraction or preparation, or be difficult to analyse directly, are ideal candidates for headspace since they can be placed directly in a vial with little or no preparation.