Silylation is the most widely used derivatization technique. Nearly all functional groups which present a problem in gas chromatogaphic separation (hydroxyl, carboxylic acid, amine, thiol, phosphate) can be derivatized by silylation reagents. It involves the replacement of an acidic hydrogen on the compound with an alkylsilyl group, for example, -SiMe3. The derivatives are generally less polar, more volatile and more thermally stable. The introduction of a silyl group(s) can also serve to enhance mass spectrometric properties of derivatives, by producing either more favorable diagnostic fragmentation patterns of use in structure investigations, or characteristic ions of use in trace analyses employing selected ion monitoring and related techniques.