Evaluating Analytical Parameters and Understanding Drug-Matrix Interactions in Forensic Hair Analysis

Previous literature suggests that there are different modes of interaction between drugs of abuse and human head hair. The ambiguity of these interactions has resulted in criticism of the routine use of hair as a biological matrix for toxicological analysis. In addition, available hair reference materials (HRM) are often poorly representative of real samples. The aims of the present research are to address these issues by comparing the most common methods to prepare hair samples for analysis and to investigate the interactions that drugs have with the hair matrix. Pretreatment steps in the analysis of drugs in human hair include decontamination, segmentation, extraction, and purification. Optimizing decontamination is essential to reduce the possibility of false positive results due to external contamination, while optimizing extraction is essential to accurately identify and quantify drugs present in a hair sample.
The first goal of this project is to evaluate standardized decontamination approaches using authentic hair specimens from drug users and externally contaminated blank human hair. The second goal is to conduct similar experiments to evaluate parameters critical to drug extraction from hair, including disruption of the hair matrix, extraction solvent and volume, and hair particle size, using incorporated HRM and HRM prepared from drug user hair. Both goals will employ a rigorous statistical design of experiments (DOE) approach to identify major factors impacting results and facilitate development of optimized methods. Drugs chosen for evaluation include methamphetamine, cocaine, heroin, morphine, diazepam, and THC. Determining effective decontamination/extraction also requires an understanding of how the drugs of interest are held in the matrix. While consensus has emerged regarding the primary routes of exposure of head hair to drugs of abuse, the nature of the physicochemical interactions between the biological matrix and these substances has not been fully explored. Thus, the third aim of this research is to determine, for specific drug classes, the relative proportion of ionic, polar non-ionic, and hydrophobic binding to hair in both drug incorporated and authentic hair from users.

This research proposes to contribute to forensic hair analysis by optimizing existing pretreatment methodology and by determining the physicochemical nature of drug interaction in hair. In addition, the research will help improve the design and production of relevant HRM in forensic toxicology. Research findings from this project will be disseminated in a doctoral dissertation, published peer-reviewed articles, NIJ reports, and in presentations at national scientific meetings.

This project contains a research and/or development component, as defined in applicable law, and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14).

CA/NCF