Using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and matrix assist-ed laser desorption/ionization mass spectrometry (MALDI-MS) for investigations on single hair samples to solve the contamination versus incorporation issue of hair analysis in case of cocaine and methadone
Drug testing in hair is a subject of controversial discussion. Claims that decontamination pro-tocols could generate false positive samples, by washing contaminations into the hair, have unsettled many toxicologists. At least for zolpidem (known for showing only minor contami-nation), it could be shown that differentiation of drug incorporated via bloodstream from con-tamination was possible. The current work addresses cocaine and methadone, known for their high concentrations and contamination issues. Longitudinally and cross sectioned sam-ples of drug-soaked hair, consumer hair and cocaine powder contaminated hair were investi-gated using time of flight – secondary ion mass spectrometry (ToF-SIMS) and matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). In addition, resulting wash solutions were investigated using LC-MS/MS. Differentiation of contamination from incorporation was possible for soaked and consumer hair samples. There, contamination could be localized in superficial compartments of the hair and could be removed using strong wash-protocols. In case of powder contaminated hair samples, a small share of cocaine re-mained in the inner structures even after application of the strongest wash protocols. Howev-er, taking into consideration the differences in behavior during decontamination steps com-pared to both, soaked and authentic hair, the validity of this contamination protocol (rubbing cocaine powder into hair) must be questioned. Furthermore, when using cut-off values and metabolite ratios (from routine hair analysis), differentiation of incorporation from contamina-tion was possible also for all our experimental samples in this study. Inclusion of metabolites as well as application of cut-off values is therefore a must in routine hair analysis.