Rapid computerized identification of compounds in complex biological mixtures by gas chromatography—mass spectrometry

Abstract

A new method has been developed for rapid identification of compounds in complex mixtures by gas chromatograph—mass spectrometer—computer system. The method uses a gas chromatographic retention index in conjunction with a small set of discriminating ions to identify each compound. The retention index predicts to within 1% the location of a time-dependent “window” within which a specific compound may appear, while the accuracy of the peak identification is dependent primarily upon the specificity of the ion set chosen. Optimum specificity is obtained by selecting ions which not only are chracteristic of the compound to be identified, but which also differentiate it from other compounds likely to elute at similar retention times. Utilizing the data files created by repetitive scanning during a single elution by gas-liquid chromatography, the present algorithm permits the automated identification of approximately eight compounds per minute. Examples of the identification of acidic urinary metabolites are given; however, the method is sufficiently general to be applied to any group of volatile compounds.