Amphetamine-type stimulants analysis in oral fluid based on molecularly imprinting extraction

A methamphetamine-based molecularly imprinted polymer (MIP) has been prepared by bulk polymerization to recognize new psychoactive substances (NPS) of the amphetamine, cathinones and 2C families in oral fluid samples, being the first precedent of a synthetized MIP for the extraction and preconcentration 32 NPS including amphetamine type substances and synthetic cathinones from oral fluids. Pre-polymerization complex and resulting materials were appropriately characterized by infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption-desorption isotherms. Appropriateness of the material for the specific recognition of the target analytes was also evaluated through computational calculations and experimentally assessed by solid phase extraction (SPE). The most appropriate SPE conditions were evaluated and recoveries of 32 different NPS were obtained, ranging from 80 to 120% with a relative standard deviation (RSD) in all cases lower than 12%. Amphetamine-related NPS were analyzed by a fast and portable methodology based on ion mobility spectrometry (IMS) and a rearguard procedure based on ultra-high performance liquid chromatography coupled to mass spectrometry (UHPLC-MS) providing limit of detection values from 10 to 80 μg L^-1 and from 0.03 to 1.3 μg L^-1, respectively. Oral fluid samples, containing different interferents like caffeine, fluticasone and cetirizine, were spiked with 300 μg L^-1 amphetamine and subsequently analyzed, showing recoveries ranging from 81 to 115% using both methodologies. Thus, this paper shows preliminary results to demonstrate the applicability of the developed procedure which could be used with minor modifications as screening technique in on-road drug analysis.