P9: A closer look to the effect of external influences on cocaine in hair using imaging mass spectrometry

Abstract

Introduction Forensic hair analysis is considered to be a standard method in identifying chronic drug users since it can give information about the time course of the substance abuse. Interpreting these results, one should be aware of all pitfalls. External contamination, decontamination protocols, cosmetic hair treatment,… They all might influence the analytical result of forensic hair analysis. Since the laborious standard extraction method used nowadays is inefficient in pointing out these pitfalls, there is an urgent need in new analysis methods that can help to unravel what is happening inside the hair. Imaging mass spectrometry is shown here as a very promising tool in studying the effect of external influences on the spatial distribution of cocaine in hair. Methods Matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI) and Metal Assisted Secondary Ion Mass spectrometry (MetA-SIMS) is used to visualize the effect of hydrogen peroxide treatment and different decontamination solvents on cocaine contaminated and users hair. Images are made on intact hair as well as cross and longitudinal sections. Cross sectioning is carried out on carboxymethylcellulose embedded hair using a microtome. Longitudinal sections are prepared using a self-designed cutting device without any use of embedding medium. Results After bleaching contaminated and users hair with hydrogen peroxide, images revealed a complete loss of detectability of cocaine (m/z 304 and 182) and its reaction products. Since all compounds of interest are found in the hydrogen peroxide and wash solution, these findings indicate that all evidence of cocaine use might be lost after a hair bleaching treatment. The comparison of different decontamination solvents shows that cocaine is most effectively removed using methanol or water. Remarkably, MALDI-TOF and SIMS images of cross and longitudinal sections of contaminated and cocaine users hair show that methanol and water also seem to influence the concentration of cocaine in the hair. SIMS images of unwashed hair are able to distinguish between external contaminated and users hair, making it very interesting as forensic evidence. Conclusion We show that imaging mass spectrometry is a very promising technique in studying the spatial distribution of drugs in hair. Being able to have a closer look to what is happening in the hair, the effect of external influences on drug incorporation and distribution can finally be solved. The presented study surprisingly shows the influence on drug distribution in the hair using certain decontamination solvents and also reveals the possibility of complete loss of forensic evidence in bleached hair.