Efficient on-site detection of nitazenes in hair: Integrating MCX pipette-tip solid-phase extraction with miniaturized mass spectrometry.

As a emerging class of synthetic opioids, nitazenes have witnessed an alarming global proliferation in the illicit drug market, posing severe threats to public health and social stability. Consequently, there is an urgent and growing demand for robust on-site rapid detection methods targeting these substances, especially within complex biological matrices. Herein, we report the first development of a miniaturized mass spectrometry (miniMS)-based analytical platform enabling rapid, on-site detection of 16 nitazenes in hair samples for the first time. Micropulverized extraction solvents and key MS parameters of the miniMS coupled with nano-electrospray ionization (nano-ESI) were systematically optimized. The limits of detection (LODs) and limits of quantification (LOQs) of miniMS for the 16 nitazenes in hair matrix ranged from 5 ng/mL to 20 ng/mL, and 20 to 80 ng/mL. Mixed-acidic cation-exchange pipette-tip solid-phase extraction (MCX PT-SPE) was successfully applied, yielding enrichment factors ranging from 6.7 to 9.9-fold across the various target analytes. Following integration with MCX PT-SPE, the miniMS method achieved a 94% true positive detection rate for 28 authentic hair samples (0.27 ng/mg to 8.56 ng/mg), represented a 38% increase compared to un-enrichment analysis. The linear ranges of individual analytes predominantly fell from their respective LOQs to 500 ng/mL, with the coefficient of determination (r2) exceeding 0.99. Precision ranged from 6.9% to 14.2% across all analytes. The Relative errors of quantitative results, calculated by comparing miniMS and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for 8 authentic hair samples, ranged from -11.3% to 18.8%. The total analytical turnaround time for one single hair sample was within 10 min, with an additional 5 min required if the enrichment procedure was implemented. Compared with conventional techniques, this method enables on-site rapid detection while offering enhanced operational simplicity, high sensitivity, and portability, thereby demonstrating promising application prospects in drug crime investigation and forensic science.