Analysis of Blood Alcohol by Headspace with Simultaneous GC-FID and MS Detection

Determination of Blood Alcohol Content (BAC) has been a standard analytical method in criminal labs for many years. The typical instrument configuration consists of a static headspace instrument for sample introduction, followed by gas chromatography (GC) with two dissimilar capillary columns for separation, and two Flame Ionization Detectors (FIDs) for detection and quantitation. Two sets of data are obtained simultaneously, and the quantitative results from the two FIDs are compared for confirmation of the reported BAC levels.

With the BAC method, compound identification is done by comparing the retention time (RT) of blood alcohol in the unknown sample to the RT obtained from analysis of an analytical standard. Recently however, additional compound identification provided by matching the ethanol mass spectrum to a library spectrum, in addition to RT, has proven to offer an additional level of confirmation. This application note describes BAC analysis using a GC-FID in parallel with a mass spectrometer (MS) for positive compound identification.