Rapid and simultaneous quantification of cocaine and adulterants in seized samples using portable NIR spectroscopy and chemometrics

The rising global cocaine trafficking and consumption, coupled with the proliferation of harmful adulterants, highlights the urgent need for rapid, reliable, and on-site analytical methods. Unlike traditional chromatography-mass spectrometry, which requires extensive sample preparation and long analysis times, near-infrared (NIR) spectroscopy offers a non-destructive, portable, and efficient alternative. A comprehensive, portable method is needed to quantify cocaine and its common, hazardous adulterants in seized samples, providing crucial information for public health and police intelligence. A portable NIR spectroscopy method combined with chemometrics for the simultaneous quantification of cocaine, phenacetin, and levamisole in 155 real seized samples was developed and evaluated. PLS1 and PLS2 models were built and validated. PLS1 models showed prediction errors (RMSEP) below 6.40% for all compounds (6.40% for cocaine, 2.93% for levamisole, and 3.38% for phenacetin), with high R² values. The streamlined PLS2 model, allowing simultaneous quantification, yielded RMSEP values below 6.55% for all compounds (6.55% for cocaine, 3.64% for levamisole, and 3.11% for phenacetin). A reproducibility study confirmed the robustness, showing relative standard deviations (RSD) below 10% in most cases for all three compounds. This work demonstrates portable NIR spectroscopy as a fast, reliable, and non-destructive screening tool for forensic analysis. This method addresses the novelty of a multi-analyte response, as existing literature focuses on individual compounds. Simultaneously quantifying cocaine and critical adulterants, provides richer insights vital for public health, informing users of risks, and enhancing police intelligence in drug trafficking investigations, thus reducing reliance on time-consuming chromatographic analyses. • First portable NIR method for simultaneous cocaine/adulterant quantification • Single PLS2 model predicts three compounds with RMSEP <6.55% using real seizures • Non-destructive analysis eliminates sample preparation and chromatography needs • Externally validated with 155 samples (0.99-88.05% cocaine concentration range) • Field-deployable alternative achieving <10% RSD reproducibility over 5 days