is a method of separating and analyzing mixtures of chemical components. Chromatography is used by large brewery laboratories to identify and quantify volatile and non- volatile beer components. Separation occurs by allowing a mixture to travel through an adsorbent matrix so that each compound is ultimately resolved into separate zones based on chemical or physical properties such as polarity, boiling point, or size. The simplest forms of chromatography include separation on paper sheets or specially coated plates or through columns packed with an inert media. Various methods are then employed to detect and identify the different resolved species.

Two sophisticated methods of chromatography are gas chromatography (GC) and high performance liquid chromatography (HPLC). Both provide separation techniques for qualitative or quantitative identification of substances.

Gas chromatography relies on selective adsorption and release (desorption) of volatile components on a stationary phase. Components in a mixture are carried through a column by an inert gas to a specific type of detector where species, via calibration with known compounds, are identified based on retention (residency) time in or on the column.

In the brewery laboratories, GC is used to separate higher alcohols (fusel oils) and esters in beer and phenols (wheat beers) and also vicinal diketones such as the buttery flavored diacetyl compound. Results are related back to the chemical composition of the beer and to its sensory properties. GC results can be used to give early warning of an infection (which may produce diacetyl above normal levels) or simply to provide a “map” of a beer’s aromatic properties. In some breweries, GC results are used to determine when a beer is ready to leave its fermenter and be put into a lagering cellar for aging; the decision would depend on diacetyl having dropped into an acceptable range of concentration.

High performance liquid chromatography uses a liquid mobile phase to transport and separate components of a mixture. Mixtures are injected under high pressure into a packed column known as the stationary phase. In the column the mixture is resolved, via adsorption and release (desorption), into its constituents. As for GC methods, different types of detectors are available for appropriate identification. Quantification is also possible via integrated calibration with known amounts of specific compounds. HPLC, unlike GC, is more suitable for separating less volatile compounds. As such it is useful in analyzing sugars in beer and wort, organic acids, and hop iso-alpha acids. Chromatography can provide highly useful information, but it is very expensive and time-consuming to perform, and therefore is rarely employed by breweries producing less than 100,000 hectoliters per year.