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

• Molecularly imprinted polymer (MIP) for cocaine recognition in plasma samples.
• μ-SPE (cone shaped) device based on porous membrane-protected containing MIP.
• Fast cocaine and metabolites determination by reverse phase HPLC–MS/MS.
• Limit of quantification lower than the cut-off values for cocaine abuse confirmation.

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 (μ-SPE). High performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) was used for quantifying the analytes after MIP-μ-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 °C) for 10 min. Analyte elution was achieved by subjecting the MIP-μ-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 μL of mobile phase, the MIP-μ-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.