Rapid colorimetric and electrochemical fingerprint detection of controlled substances using a safe, dual-mode redox-sensitive universal reagent

Rapid and safe detection of controlled substances is essential for forensic practice. We developed an aqueous bicinchoninic acid‑copper (II) (BCA-Cu 2+ ) reagent prepared in sodium carbonate and borax that supported dual mode colorimetric and electrochemical detection of a broad range of analytes. The reagent generated clear time-dependent colorimetric responses for stimulants, opioids, cannabinoids, pharmaceutical adulterants, drug mixtures and proteins. Cyclic voltammetry produced reproducible electrochemical fingerprints for all tested analytes, including those that produced weak or no visible colorimetric change, and enabled discrimination between structurally related drugs. Quantitative performance was evaluated using 3,4-Methylenedioxymethylamphetamine (MDMA) as a model analyte and the colorimetric response at 564 nm was linear from 6.6 to 60.0 μg/mL with a limit of detection of 0.01 μg/mL. Interferent testing showed that several common diluents, thiol-containing compounds and metal ions produced measurable colorimetric response but their voltammetric fingerprints remained distinguishable from those of the drugs. Seized Ecstasy and heroin samples produced colorimetric behaviour and cyclic voltammetric fingerprints that were consistent with their GC–MS identified constituents, demonstrating compatibility of the reagent with real case seized materials. The reagent was non-corrosive, stable over extended storage and compatible with low-cost handheld potentiostats. These findings present a safe and versatile platform that integrates rapid colorimetric screening, quantitative drug detection and electrochemical fingerprinting within a single aqueous system suitable for on-site forensic applications. • Acid-free, non-carcinogenic BCA-Cu 2+ reagent enables safe, field-deployable detection of illicit drugs. • Dual-mode detection integrates rapid colorimetric screening with confirmatory electrochemical fingerprinting. • Distinguishes structurally similar drugs via unique anodic and cathodic CV peak profiles. • Validated on seized drug samples, demonstrating high accuracy and reproducibility in operational settings. • Extended capability for protein detection under prolonged incubation, broadening forensic and clinical utility.