Synthesis and characterization of molecularly imprinted polymers for the selective extraction of cocaine and its metabolite benzoylecgonine from hair extract before LC–MS analysis

Abstract

A molecularly imprinted polymer (MIP) was synthesized and evaluated for the selective extraction of cocaine (COC) and its main metabolite benzoylecgonine (BZE) in hair extracts. To this end, a screening of different conditions of synthesis was performed by changing the nature of the crosslinker, and the functional monomer and also by changing polymerization's initiation mode. The selectivity of the different MIPs was evaluated by comparing the retention of COC and BZE between the MIP supports and also compared to a non-imprinted polymer for each. All the supports were selective for one or both molecules, but, the best results in terms of selectivity and retention were obtained for a MIP using methacrylic acid as functional monomer, ethyleneglycol dimethacrylate as crosslinker, and a photochemical initiation. An optimized procedure in acetonitrile media was developed for the selective extraction of COC and BZE with a recovery close to 80% for both molecules from the MIP. The capacity of the MIP for COC retention was also evaluated, and MIP showed a specific capacity of 8.96μmolg−1. Finally, the potential of this material for sample clean-up was demonstrated by the selective extraction of both COC and BZE from acetonitrile hair extracts spiked at the cutoff value for COC in hair analysis. By the selective purification with the MIP, a limit of quantification inferior to 0.07ngmg−1 of hair was reached for both molecules.