New psychoactive substances (NPS) pose major challenges to public health and forensic science owing to their structural novelty, chemical diversity, and rapid market turnover. Hair is a valuable matrix for drug testing, providing long term retrospective identification of repeated NPS exposure. This structured narrative review evaluated analytical methods published between 2002 and 2024 for four prespecified NPS classes in hair: synthetic cannabinoid receptor agonists (SCRAs), synthetic opioids, synthetic cathinones, and phenethylamines. A structured PubMed search was conducted using predefined eligibility criteria based on the Population–Concept–Context (PCC) framework. Data extraction included bibliographic information and methodological variables: hair source and anatomical site collection, segmentation, sample mass, decontamination, homogenization, extraction conditions, chromatographic separation, mobile phase composition, instrumental platform, analytical sensitivity, and matrix effects. Overall, 50 articles were included; 27 (54%) appeared during 2019–2024. Head hair was the most frequently hair type (n = 47; 94%), while 3-cm segments were the most common segmentation length among studies performing segmental analysis (n = 7/16; 44%). Decontamination was performed in all, but one study and most extraction systems included methanol (68%). Among the 44 studies using liquid chromatography (LC), targeted LC–tandem mass spectrometry (LC–MS/MS) predominated (n = 37; 84%). Limits of detection (LODs) ranged from 0.003 to 600 pg/mg, while limits of quantitation (LOQs) ranged from 0.011 to 1800 pg/mg and matrix effects included ion suppression and enhancement. Hair analysis remains essential for retrospective NPS detection; however, more complete reporting and analyte-specific validation are needed to improve cross-study comparability and interpretation.
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Pinheiro et al. (2026) studied this question.