A method for forensic identification of vegetable oil stains - Rapid analysis of carboxylic acids with methyl esterification using purge-and-trap gaschromatography/mass spectrometry

A simple method using purge-and-trap gas chromatography[mass spectrometry ( P&T-GC/MS) for forensic examination of oil stains was studied. Carboxylic a cids, chosen as target components for discrimination of oil samples, were e xtracted from stains with ether, methyl esterified by tetramethylammonium h ydroxide, and analyzed by P&T-GC/MS. Vegetable oils were discriminated acco rding to, their carboxylic acid compositions. Carboxylic acid composition w as independent of the substrate material of the stain. Although the carboxy lic acid composition of the oil changed on exposure to sunlight, identifica tion of oil was possible for oil stains that had been in the shade, if anal ysis was made within 20 days.