Encyclopedia of Chromatography. Cazes J, ed., New York: Dekker Encylopedias, Taylor and Francis Group, 2005 Jun; :1-9
Headspace sampling is a type of analysis in which the volatile analytes are separated from a sample matrix prior to their introduction into a gas chromatograph (GC). The gaseous phase or "headspace" above the sample matrix within a sealed system is collected and then analyzed by the GC. Headspace sampling represents an indirect method to measure volatile components of the sample matrix, that is, the gaseous phase above a sample matrix is measured, not the sample matrix itself. In the general technique, an aliquot of gas (vapor) phase sampled is in equilibrium with the liquid or solid phase of the sample matrix. In equilibrium, the distribution of the analytes between the two phases is dependent upon their partition coefficients; thus, the quantity of the original analyte in the sample can be determined from the analytical results of the headspace aliquot. Dynamic (purge-and-trap) and static headspaces are the two main classic types of headspace sampling techniques currently used. In the last decade, solid-phase microextraction (SPME) has also been developed to sample headspace volatile components. An equilibrium is established between the gas phase above the sample matrix and the solid-phase of the SPME fiber in SPME. Applications of headspace sampling are extensive and include the analysis of volatile components in the food and flavor industry, pharmaceuticals, cosmetics, biomarkers of chemical exposure or ingestion, environmental testing, and volatile monomers from plastics. Headspace sampling and analysis represent a broad analytical field with continued growth in numerous applications.