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One of the most serious limitations of the gas-chromatography is the impossibility to analyze not easily volatilized and non volatile matters directly, since they don't reach the detector at all and besides they contaminate the instrument. The work-up procedure of such samples with the aim of separating a not easily volatilized matrix is usually coupled with badly reproducible losses of the volatile analytes. When the matrix is aqueous, another problem crops up.

Many nonpolar stationary phases, as they are e.g. used in the gas-chromatography of organic solvents, are destroyed by the injection of aqueous samples. All these problems are solved by the headspace technique:

In this case we don't inject the whole sample including the matrix, but only the head space above, which always contains a certain portion of the volatile substances in the sample. How large this portion is depends - if the head space and the matrix are balanced - only on the temperature, the pressure and the steam pressure of the analytes as well as on its solubility or its adsorption behaviour in the matrix.

Headspace analysis technique