Ethylphenidate determination in oral fluids by molecularly imprinted polymer extraction and ion mobility spectrometry

Drug abuse can be easily determined by oral fluid analysis, which allows the identification of the parent compounds instead of their respective metabolites, thus reducing potential misidentifications in other biological matrices. A molecularly imprinted polymer (MIP) has been synthetized by bulk polymerization to be employed in the selective extraction of ethylphenidate, a new psychoactive substance, in oral fluids. Ethylphenidate was employed as template molecule for the synthesis of MIP, and a non-imprinted polymer (NIP) was also synthesized. Scanning electron microscopy, nitrogen adsorption measurements and infrared spectroscopy were performed to characterize the resulting materials. A simple procedure was proposed based on the use of MIP as solid-phase extraction (SPE) sorbent for the target analytes in oral samples, followed by its determination by ion mobility spectrometry, providing a selective and sensitive methodology useful for a fast drug abuse identification. Selectivity of the MIP was evaluated by the extraction yield obtained for phenidate analogues and other conventional drugs, showing a reduced affinity for MIP material. The proposed ion mobility spectrometry (IMS) procedure has been validated in terms of selectivity, sensitivity, trueness, and precision, giving a limit of detection of 20 µg L −1 and quantitative recoveries from 82 to 91% in ethylphenidate spiked oral fluid samples.