Influence of bleaching on stability of benzodiazepines in hair

In order to study the influence of hair bleaching on benzodiazepines concentrations, hair was treated with a bleaching product (Poly Blonde, Schwarzkopf & Henkel) for 20 min. The treated hair specimen was obtained from a person who died after an overdose of several illicit drugs associated with benzodiazepines. Bleached and non bleached hair were washed (acetone and water), pulverised and then incubated for 2 h in a thioglycolic solution. In the extracts obtained by solid-phase extraction on C18 columns, the different drugs with the corresponding deuterated standards were derivatized and determined by GC-MS in a SIM mode. These results show that the concentrations of all the drug detected decreased in bleached hair in comparison with non treated hair. Whereas the diminution was less important for cocaine and benzoylecgonine (decrease of 24.6 and 36.4%, respectively), concentrations for codeine, 6-monoacetylmorphine and morphine decreased more significantly (decrease of 57.5, 88.6 and 67.4%, respectively) as well as those of diazepam, nordazepam and 7-aminoflunitrazepam (decrease of 39.7, 67.7 and 61.8%, respectively). The results in this study agree with those of other authors that bleaching affects the stability of cocaine and opiates incorporated in hair. These findings also point out that bleaching influences the stability of entrapped benzodiazepines in hair. Finally, these results reconfirm that it is very important to consider the cosmetic history of a hair sample in the interpretation of hair analysis results.