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How does headspace analysis prepare a liquid sample for gas chromatography?

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Viking 1 on Mars — sample preparation Viking 1's sample scoop, poised to extract material from the surface of Mars.

Headspace analysis is a specialized sample preparation technique used in gas chromatography to isolate volatile analytes from a complex liquid matrix.

Rather than injecting the liquid sample directly, this method relies on the principle of thermal evolution. The liquid sample is placed in a sealed container and allowed to reach equilibrium. Because the distribution of the analyte between the liquid and the gas phases is temperature-dependent, the volatile components migrate into the atmosphere above the liquid surface. This equilibrated atmosphere—the "headspace"—is then sampled and injected into the gas chromatograph for analysis.1

By sampling only the vapor phase, this technique effectively removes the bulk of the sample matrix, which prevents non-volatile interferences from entering the separating column. This makes headspace analysis a highly effective tool for analyzing volatile organic compounds in various liquid samples.1