Forensic hair analysis is commonly used in forensic toxicology with regards to drug-facilitated crime, workplace testing, and post-mortem investigation. Hair as a matrix benefits these types of analyses because of its long window of detection, allowing for a determination of drug history of exposure. However, there are currently no standards for forensic hair testing methods or practices, causing bias and inconsistency in forensic hair testing across multiple laboratories. Thus, two of the three aims of this research involved systematically comparing decontamination, pretreatment, and extraction methods to develop optimized forensic hair analysis protocols for multiple drugs and metabolites. Additionally, as hair is a complex matrix, there is limited understanding regarding the physicochemical interactions that occur between drugs of abuse and hair matrix components. Thus, the third aim of this research was to assess relative levels of ionic and non-ionic interactions between drugs and metabolites and the hair matrix.
Major findings of this work included an optimized forensic hair analysis method for multiple drugs and metabolites including decontamination using one 30-min wash with HPLC water followed by three 30-min washes with dichloromethane, pulverizing the hair into a powder, and a 2-h extraction in a 12.5 µL/mg mixture of methanol acetonitrile, and 2 mM ammonium formate (25:25:50, v/v/v) at 37⁰C. In addition, binding studies indicated that almost all drugs and metabolites are involved in some degree of both ionic and non-ionic interactions with the hair matrix.
These findings will impact the forensic science community by presenting an optimized forensic hair analysis for drugs and metabolites, as well as providing additional insight regarding the interactions between drugs and metabolites and hair matrix components.