Metal-Analyte Interactions in the Forensic Detection of Psychoactive Compounds: A Narrative Review.

The continuous diversification of psychoactive substances and the complexity of forensic samples create an increasing demand for rapid, sensitive, and portable analytical approaches complementary to conventional chromatographic and mass-spectrometric methods. Interactions between psychoactive compounds and metals offer versatile detection mechanisms by converting molecular recognition, adsorption, redox reactions, and interfacial processes into measurable analytical signals. This narrative review summarizes the principal applications of metal-analyte interactions in the forensic analysis of psychoactive compounds, ranging from classical presumptive color tests and spectrophotometric and luminescence methods to metal-based nanoprobes, surface-enhanced Raman spectroscopy (SERS), and electrochemical sensors. This review emphasizes the analytical role of metals rather than individual classes of psychoactive substances. The metal-containing species and materials considered include free metal ions, coordination complexes, and redox-active species, as well as metallic nanoparticles, quantum dots, metal oxides, metal-organic frameworks, and metal-containing components of modified electrode surfaces, which participate in analyte recognition and signal generation through coordination, ion association, redox processes, adsorption, charge transfer, plasmonic enhancement, and electrocatalysis. Recent developments demonstrate remarkable improvements in sensitivity and compatibility with portable instrumentation. However, translation into routine forensic practice remains limited by matrix effects, selectivity, reproducibility, and insufficient validation with authentic samples. Understanding the underlying metal-analyte interactions is therefore essential for transforming promising sensing concepts into reliable forensic analytical platforms.