Nail analysis for the detection of drugs of abuse and pharmaceuticals: a review

Abstract

Nails can stably accumulate substances for long periods of time, thus providing retrospective information regarding drugs of abuse and pharmaceutical use. Nails have several advantages over the conventional matrices, such as blood and urine, including a longer detection window (months to years), non-invasive sample collection, and easy storage and transport. These aspects make nails a very interesting matrix for forensic and clinical toxicology. Because of the low concentrations of drugs of abuse and pharmaceuticals present in nails and the complexity of the keratinized matrix, analytical methods need to be more sensitive, and sample preparation is crucial. This review summarizes the literature regarding the detection and quantification of drugs of abuse and pharmaceuticals in nails, as well as the employed pre-analytical and analytical techniques. Additionally, the applications of nail analysis are reviewed. Finally, an overview of the challenges of nail analysis is provided, and guidelines for future research are proposed.

Myth debunked: Keratinous pangolin scales do not contain the analgesic tramadol

“…We collected the keratin samples using standard human fingernail clippers from the scales of museum specimens (Table 1; Supporting Information Data S1). Because we are addressing whether or not tramadol might be produced or synthesized within the keratin matrix of scales, and surface contamination would confound the results, each keratin clipping was washed prior to analysis (Cappelle et al, 2014;Pinho et al, 2013). Each clipping was washed in a 2.0 mL tube with distilled water and sonicated for 10 minutes.…”

Quantitative mass spectrometry of unconventional human biological matrices

“…Thus, alternative methods of extraction are occasionally implemented; for example, ultrasound-assisted extraction with methanol (after micropulverization of the specimen) [50,51]. To remove matrix interferences (especially after digestion), subsequent clean-up by solid-phase extraction (SPE) is necessary [48]. In fact, such extensive preparation of hair and nail specimens is laborious, time-consuming and may introduce errors to the final result [52].…”

“…For example, some drugs bind to melanin, which contributes to higher concentrations of those drugs in dark hair than in lighter-coloured hair [3]. The advantage of analysis of nails (when compared with hair) is the lack of the possible bias due to different melanin content in the specimens obtained from different individuals [48].…”

Evaluation of drug incorporation into hair segments and nails by enantiomeric analysis following controlled single MDMA intakes

“…Because toenails grow slower than fingernails [10,11,9], they represent a longer window of detection for drugs. Therefore, higher drug concentrations in toenail samples may be explained by drug use long time prior to the study.…”

“…Nails, another keratinzed matrix, are being discussed as an alternative to hair because nails also accumulate drugs [9][10][11][12][13][14][15]. Investigations on paired hair and nail analysis for amphetamines delineated similar [16] or higher concentrations in hair [17], but one group reported slightly higher amphetamine concentrations in fingernails compared to hair [18].…”