Biosampling strategies for emerging drugs of abuse: towards the future of toxicological and forensic analysis

The term "new psychoactive substances" refers to emerging drugs of abuse whose chemical structure and psychoactive effects are similar to other already known compounds, often providing a "legal" alternative to internationally regulated drugs and mostly available via on-line retail sites. There are several categories of new psychoactive substances, such as synthetic cannabinoids, cathinone analogues, phenethylamines, tryptamines, and the need to identify and quantify an unprecedented and growing number of new compounds represents a unique challenge for toxicological and forensic analysis. The purpose of this review is to highlight biosampling, sample preparation and analysis of the most important classes of emerging drugs of abuse in biological matrices, focusing on alternatives to classical blood and urine "in tube" approach, still representing the standard routine for bioanalysis, despite inherent flaws regarding handling, stability and process feasibility. Chromatographic techniques coupled to mass spectrometry are usually exploited to identify and quantify new psychoactive substances; due to their high sensitivity and selectivity, it is possible to determine low concentrations not only in plasma and urine, but also in alternative matrices like dried blood spots, oral fluid, hair, other body fluids and tissues. Current literature on analytical methodologies applied to these samples is still limited and a more thorough validation is often required, including a comparison among the results obtained from conventional approaches and from innovative strategies, in order to determine their actual suitability.