Analytical Detection and Sample Preparation Techniques for Selected New Psychoactive Substances: Advances, Critical Limitations, and Future Perspectives.

New psychoactive substances (NPS) present a rapidly evolving challenge for forensic and clinical toxicology because newly introduced compounds may remain undetected by conventional analytical panels or become difficult to identify after metabolism, degradation, or matrix-related interference. This review critically evaluates 41 original research studies issued between 2020 and 2026 on sample-preparation and analytical detection strategies for selected NPS, particularly synthetic opioids, synthetic cathinones, synthetic cannabinoids, and designer benzodiazepines, with emphasis on the factors governing the reliability, adaptability, and interpretive value of toxicological workflows. To the best of our knowledge, this is the first review to comprehensively integrate and critically assess both sample-preparation procedures and instrumental detection methods across the major classes of NPS. The reviewed evidence indicates that analytical sensitivity alone is insufficient to ensure reliable identification. Method performance depends on the interaction between extraction selectivity, matrix compatibility, analyte stability, metabolite selection, chromatographic resolution, and the scope of instrumental screening. Targeted methods remain highly effective for the confirmation and quantification of known compounds, whereas high-resolution and complementary screening approaches provide greater flexibility for detecting newly emerging substances and retrospectively examining previously acquired data. Nevertheless, broad detection capability must be supported by robust validation and sufficient structural evidence to avoid uncertain or incomplete identification. Future analytical strategies should therefore integrate targeted and non-targeted approaches, strengthen metabolite-informed detection, improve reference and spectral resources, and prioritize matrix-specific validation using authentic specimens. Such coordinated workflows are essential for producing timely, adaptable, and scientifically defensible results in emerging-drug toxicology.