The effectiveness of decontamination procedures used in forensic hair analysis

Abstract

Hair is a mainstream specimen used in forensic toxicology to determine drug use and exposure. However, the interpretation of an analytical hair result can be complicated by the presence of external drug contamination. Decontamination procedures are included in hair analysis methods to remove external contamination, but the capacity of these washes to completely remove contamination for all drugs is controversial. It is evident that there is no consensus on the most effective decontamination procedure, nor can decontamination procedures consistently remove external drug contamination to less than reportable cut-offs for all analytes. ∆-tetrahydrocannabinol deposited from cannabis smoke is mostly removed by organic solvents, whereas ionizable drugs are more effectively removed by an aqueous wash. Organizations such as the Society of Hair Testing recommend a hair decontamination procedure should include both an organic and aqueous washing step, which is in accordance with the reviewed literature. Studies involving a systematic evaluation of various solvents have shown that the most effective organic solvent was methanol and the most effective aqueous solvent contained sodium dodecyl sulfate detergent. If future systematic studies can demonstrate similar findings, a consensus on the most effective decontamination procedure for forensic hair analysis may be established.

Hair analysis for New Psychoactive Substances (NPS): Still far from becoming the tool to study NPS spread in the community?

“…It is known that the keratinized hair shaft has a complex, multi-compartment structure and the drug incorporation in hair is a function of the acidity/basicity of the compound, its lipophilicity, and its affinity to melanin [ 72 ]. On the other hand, the main factors that influence drug incorporation in hair, affect the drug extraction from hair, as well [ 73 ]. Therefore, the extraction procedure poses several issues most relevant to the complexity of this matrix.…”

“…Of main concern to the toxicologists is the removal of the external contaminations from hair, consisting of organic and inorganic chemicals that have been deposited to the hair shafts, by applying appropriate washing steps. The hair washing steps are usually applied according to the suggested guidelines which states further that external contamination must be considered to interpret findings, while researchers should evaluate the efficiency of washing procedures [ 73 , 74 ]. Nevertheless, some of the reviewed studies herein, reported extensive washing procedures, and others none, indicating the different viewpoints for the necessity of this step, especially in respect to differentiate the active drug use from external drug deposition onto hair.…”

“…This preference should be attributed, firstly, to its ability to extract from hair very diverse classes of NPS, and secondly, to the simplicity of the relevant procedures, as compared to SPE, or other LLEs. However, the extraction with acidified methanol presents the disadvantages of yielding lower drug recoveries compared to other procedures, and of resulting in a high degree of contamination from hair matrix (matrix effect) [ 72 , 73 ]. In fact, matrix decontamination is one of the main limitations in hair testing, with an impact on extraction efficiencies and on the LODs/LOQs of the analytes.…”

Forensic toxicological analysis of hair: a review

“…Society of Hair Testing recommends that a hair decontamination procedure should include both an organic and aqueous washing step. Studies have shown that the most effective organic solvent was methanol and the most effective aqueous solvent contained sodium dodecyl sulfate detergent (Mantinieks et al 2018).…”

Determination of steroids in bovine hair: Validation of a microwave‐assisted chemical derivatization method using liquid chromatography–tandem mass spectrometry and in vivo studies

“…Before sample extraction, a decontamination procedure is recommended to be performed in a washing step that includes both an organic and an aqueous phase. In that way, any external contaminant, which could lead to a false‐positive result, must be washed away, without removing the target analytes 10 . The next step in sample preparation is the homogenization with the aim of increasing the surface area exposed to the extraction agents, usually executed by cutting hair into small pieces or by grinding, for example, in a ball or cryogenic mill 11 .…”