Mass spectrometry (MS) is the 'gold-standard' in forensic science for the identification of drugs because each has a unique 'fingerprint' (i.e. mass spectrum). The interfacing of MS with separation techniques such as gas chromatography (GC) and liquid chromatography (LC) enable complex mixtures, such as extracts of horse urine, to be analysed.

The Australian Rules of Racing permit the use of drugs provided no trace of these drugs can be detected in urine or blood collected on race day. Penalties for noncompliance with 'drug-free racing' can be severe as the horse's trainer is held responsible any prize money may be lost.

During 1994, the Australian Jockey Club Laboratory analysed 10,174 urine and 2,191 post-race blood samples. Each sample was subjected to a variety of different extraction methods and all extracts were analysed by GCMS. Less than 0.5% contained a drug, or drug metabolite.

In order to process this large sample load by GCMS strategies have been developed which include the compositing of samples and overnight computer controlled auto injection and processing of sample extracts. The MS may operate in the El, positive or negative CI, or MS/MS mode dependent upon the drugs targeted by each extract.