The Forensic Determination of Drugs of Abuse Using Liquid Chromatography with Electrochemical Detection: A Review

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Abstract
The identification and quantitation of drugs of abuse in biological fluids, bulk pharmaceuticals and illicit preparations requires a large commitment of manpower and time within most full service forensic science laboratories. Funding levels within such laboratories rarely allow for large expenditures for very expensive or esoteric equipment, so the majority of the analyses of controlled substances must be performed using techniques which are relatively inexpensive, yet which provide for accurate and sensitive determinations of such compounds in a variety of matrices. Chromatographic methods provide an inexpensive, yet powerful, approach for the identification and quantitation of controlled substances. Liquid chromatography (LC) is particularly well suited for the analysis of a number of important controlled substances which are relatively nonvolatile, or thermally unstable. However, the full potential of LC in the forensic analysis of drugs has not been met to date, due to the lack of suitably sensitive and selective detectors for these compounds. Electrochemical (EC) detection in liquid chromatography (LCEC) offers excellent sensitivity and selectivity for those classes of compounds which possess a suitable electrophore (redox center) in their structures. To date, LCEC has been successfully utilized for morphine and a number of related narcotics, several benzodiazepines, cannabinoids and hallucinogens, fentanyl, and a few tricyclic anti-depressants. Under carefully controlled experimental conditions, or through the use of post-column photolytic derivatization, LCEC can be expanded to allow for the trace determination of cocaine, barbiturates and many more benzodiazepines. In this manuscript we will examine the use of LCEC for the analysis of controlled substances, evaluate the strengths and weaknesses of the approach, and discuss possible future trends in the use of LCEC in the forensic examination of drugs of abuse.