Analysis of hydroxy-cocaine metabolites as evidence of cocaine consumption: Identification by parent ion search and quantitation by UHPLC-MS/MS in hair

Abstract

Over the last decade, hair analysis has become a routine procedure in most forensic laboratories and, complementary to blood and urine, hair is a unique biological matrix which gives the opportunity to establish a temporal consumption profile. Despite hair is widely used to identify drug use, environmental contamination continues to represent a challenging factor of this procedure, especially for cocaine (COC). In the last few years several strategies have been proposed in order to distinguish between actual use and external contamination, however the commonly detected COC metabolites probably are insufficient for demonstrating cocaine use through hair testing. Thus, the aim of this study is to develop an ultra high performance liquid cromatography - tandem mass spectrometry (UHPLC-MS/MS) method able to detect and quantify hydroxy-COC metabolites, as specific markers of COC abuse, in hair samples from COC consumers, thus enabling unambiguous evidence of COC consumption. At the beginning, since no commercial reference materials were available, COC‐positive hair samples were tested using parent ion scan-based analysis to extract hydroxy COC metabolites target ions. Once identified, the reference materials were synthesized by our analytical laboratory allowing the development of the first UHPLC-MS/MS validated method to quantify p‐ and m‐isomers of hydroxy COC, as well as hydroxy benzoylecgonine (BE) and hydroxy norcocaine (NCOC). The method was successfully applied to a large number of COC-positive hair samples and introduced into a routine procedure for testing drug ingestion in order to evaluate for the first-time hydroxy metabolites of COC ranges in hair and their correlation with COC and BE.