Improved screening capabilities in forensic toxicology by application of liquid chromatography–tandem mass spectrometry

Abstract

The introduction of the upcoming instrumentation liquid chromatography–mass spectrometry (LC–MS) into the field of forensic toxicology was primarily focused on crucial substances, undetectable by current analytical techniques. Typically, polar substances (which cannot be derivatised properly) thermolabile and high molecular weight compounds were first targets of the analytical technique. Successful application of LC–tandem mass spectrometry (API 2000, Applied Biosystems) in multiple reaction monitoring (MRM) mode to the identification of alprazolam (>1 pg/mg), dothiepine (>0.4 pg/mg) and piritramide (>2 pg/mg) in hair is presented in this paper. Moreover, the quantification of cocaine and benzoylecgonine was performed in the grey zone of suspicious hair samples (66 cases with positive response below cut-off in immunoassay screening but negative GC–MS confirmation). A high correlation between both techniques and a reliable substance confirmation by LC–MS–MS could be verified down to cocaine concentrations of 20 pg/mg in hair. An extension of the concept of MRM experiments to larger groups of analytes was attempted successfully. An adaptable combination of experiment modules (e.g. stimulants, narcotics, benzodiazepines, antidepressants/neuroleptics) to screening methods provides an efficient tool for a sensitive and specific systematic toxicological analysis (STA) in ‘general unknown’ cases.