A systematic investigation of forensic hair decontamination procedures and their limitations

Abstract

The effectiveness of decontamination procedures used for the removal of external drug contamination in forensic hair analysis is an ongoing debate. This investigation evaluated wash methods complying with Society of Hair Testing (SoHT) guidelines and their capacity to remove cocaine (COC) and methamphetamine (MA) from artificially contaminated hair. The most effective decontamination method was determined using a systematic approach, involving (1) an initial washing solvent screen, (2) optimization of wash duration, (3) comparison of sequential wash methods, and (4) reanalysis of clinical hair samples. For analysis, hair was subjected to micro‐pulverized methanolic extraction prior to quantitation by ultra‐high performance liquid chromatography−tandem mass spectrometry (UHPLC−MS/MS). Methanol (MeOH) and 0.1 M phosphate buffer (pH 6) were the most effective organic and aqueous solvents, respectively, removing 28%–38% of COC and 16%–31% of MA. Wash durations longer than 30–60 minutes did not remove additional amounts, and a more efficient sequential wash method was subsequently developed. Despite this, the interpretation of reportable results relative to the SoHT cut‐off levels was unchanged for most clinical hair samples reanalyzed after washing by agitation for 30 minutes with MeOH. These findings highlight the inability of decontamination solvents to completely remove external COC and MA contamination from hair, including wash methods adhering to SoHT guidelines.

Mapping the Chemistry of Hair Strands by Mass Spectrometry Imaging—A Review

“…As removing surface contamination is especially important in MSI analysis of the hair cuticle, sample preparation methods usually include washing procedures similar to those for bulk analyses [110,111]. A variety of decontamination procedures have been proposed, including washing with methanol, ethanol, dichloromethane, isopropanol, or buffers [36,37,[115][116][117][118][119]. However, many methods might lead to the loss of several elements and molecules, affecting total concentrations [12,115].…”

Weekly and Longitudinal Element Variability in Hair Samples of Subjects Non-Occupationally Exposed

“…Before performing the analysis, the authors worried about the effects of cleaning and cutting hair before sampling. The problem of hair cleaning is largely discussed as well as the effect of washing using different procedures, as reported in the literature [56][57][58][59][60][61][62]. The IAEA recommends a cleaning procedure for hair [47].…”

Insights into the Decontamination of Cocaine-Positive Hair Samples

“…On the one hand, these protocols aim to remove any dirt tampering with analytics, and on the other hand, they should remove those contaminating incorporations. Different decontamination protocols were published and have been discussed in the hair analytics community, but no consensus on a universal protocol has been reached so far (3)(4)(5)(6). The present publication focuses on the suitable and proper decontamination of hair after cocaine consumption.…”

“…Thus, interpretation of measured cocaine concentrations in hair is highly debated in the scientific community. A recent publication from Mantinieks et al systematically investigated decontamination procedures and their limitations in regard to cocaine ( 3 ), whereas Tsanaclis et al have provided a comprehensive review discussing the practical approach for interpreting the results in case external cocaine contamination is in question ( 6 ). In another recent publication, it was shown, using mass spectrometric imaging, that recent contaminations accumulate mainly in superficial hair compartments, where they are more easily washed out than cocaine incorporated into inner hair compartments ( 8 ).…”