تسجيل الدخول

تسجيل

Gas chromatography and gas , chromatography–mass spectrometry

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  276

2026-10-24

43

Gas chromatography and gas

chromatography–mass spectrometry

Gas chromatography has been the workhorse analytical technique of most doping testing laboratories for many years. Originally GC was combined with flame ionisation detection (FID), nitrogen-phosphorus detection (NPD) and, for some drugs, electron capture detection (ECD). The advent of relatively inexpensive benchtop GC-MS instruments has made GC-MS the analytical technique of choice where analytes are amenable to chromatographic separation by GC. GC offers the capability of separating a large number of substances in a single analytical run making it ideal for screening purposes. Operation of mass spectrometry in selected-ion monitoring (SIM) mode gives enhanced sensitivity, while operation in scan mode enables the mass spectrum of a drug identified in a sample to be assessed for match against the mass spectrum of an authenticated standard of the drug. It may also be possible to identify, presumptively, unexpected and/or interfering substances using mass spectral libraries or, in some instances, comparison with literature spectra. As noted previously, caution must be exercised when analysing by GC drugs that are excreted in urine as conjugates and an appropriate method of hydrolysis must be incorporated into the analytical procedure. Various derivatisation procedures are employed to make polar and/or thermally labile analytes more amenable to analysis by GC.

Anabolic steroids, which are difficult to chromatograph without chemical conversion, are normally silylated and analysed as trimethylsilyl derivatives. Derivatisation has also been found to be useful for the analysis of drugs that do not produce characteristic ions without chemical conversion.