Determination of cocaine and its metabolites in plasma by porous membrane-protected molecularly imprinted polymer micro-solid-phase extraction and liquid chromatography-tandem mass spectrometry

A selective molecularly imprinted polymer synthesized for the selective retention of cocaine (COC) and its metabolites [benzoylecgonine (BZE), ecgonine methyl ester (EME), and cocaethylene (CE)] was used as a solid adsorbent for assessing cocaine abuse by plasma analysis. The MIP beads (50 mg) were loaded inside a cone shaped device made of a polypropylene (PP) membrane for micro-solid-phase extraction (mu-SPE). High performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used for quantifying the analytes after MIP-mu-SPE. The best retention capabilities were reached when loading plasma samples (within the 0.1-5.0 mL range), previously adjusted to pH 5.5 by orbital-horizontal shaking (150 rpm, 50 degrees C) for 10 min. Analyte elution was achieved by subjecting the MIP-mu-SPE device to ultrasound (37 kHz, 325 W) with 10 mL of dichloromethane/2-propanol/ammonium hydroxide (76:20:4) for 8 min. After eluate evaporation to dryness and re-dissolution in 100 mu L of mobile phase, the MIP-mu-SPE method yielded a pre-concentration factor of 50. Precision was assessed by intra-day and inter-day assays, and accuracy (intraday and inter-day analytical recovery, as well as the analysis of a BTMF 1/11-B control serum sample) show that the developed method is highly precise and accurate. In addition, the limits of detection, ranging from 0.061 ng mL(-1) for COC to 0.87 ng mL(-1) for BZE, were low enough for confirmative conclusions regarding cocaine abuse. The method was used for screening/quantifying cocaine and metabolites in plasma samples from poly-drug abusers. (C) 2016 Elsevier B.V. All rights reserved.