Screening and identification of drugs in human hair by high-performance liquid chromatography—photodiode-array UV detection and gas chromatography—mass spectrometry after solid-phase extraction a powerful tool in forensic medicine

Abstract

A method is described to screen for a wide range of pharmaceuticals in human hair, 75 mg of powdered hair are incubated (12 h at + 56°C) in 2 ml of distilled water (acidic compounds) or 0.1 M hydrochloric acid (neutral and basic compounds). A twin solid-phase extraction on C 18 cartridges is used for the sample clean-up procedure. Acidic drugs are fixed at pH 2 and eluted with 1% ammoniacal methanol while neutral and basic drugs are retained on the column at pH 8.6 and eluted with methanol containing 0.5% acetic acid. The internal standard (I.S.) for the acidic extraction was bupivacaine while the I.S. for the basic extraction was prazepam. The separation of the drugs was performed using both the liquid and the gas chromatographic techniques whereas identification was achieved using photodiode array and mass spectrometric detection, respectively. The liquid chromatographic system gives an elution of the drugs following a multi step gradient from a Symmetry C 8 (Waters) 5 μm column (250×4.6 mm I.D.) at +30°C with acetonitrile-phosphate buffer (pH 3.8). Identification is achieved using the reference data (retention times and spectra) of 675 pharmaceuticals, toxicants and drugs of abuse stored in a personal library. The present method has been applied during 6 months in our laboratory. By establishing a victim's drug use history, it is a very powerful tool in forensic medicine. We illustrate the method with some real cases of police crime investigation.