Determination of lidocaine in hair of drug fatalities by headspace solid-phase microextraction

The local anesthetic lidocaine was determined in hair by hydrolysis of the samples with 4% NaOH in the presence of excessive Na2SO4 and subsequent headspace solid-phase microextraction with a 65-microm Carbowax/divinylbenzene fiber, and gas chromatography-mass spectrometry measurement with etidocaine as the internal standard. The calibration curve was linear between 0.1 and 1000 ng/mg. The detection and quantitation limits were 0.1 and 0.4 ng/mg, respectively. The method was applied to hair samples of 49 drug fatalities, and positive results were obtained in 32 cases with lidocaine concentrations between 0.4 and 400 ng/mg and 675 ng/mg in one extreme case. For comparison, morphine, 6-acetylmorphine, codeine, dihydrocodeine, methadone, cocaine, and benzoylecgonine were also determined by usual methods. From segmental investigations in four of the cases and from comparison with the hair concentrations of the other drugs, it follows that lidocaine was consumed for a longer period of time as an adulterant of cocaine and heroin preparations.