We report the on-line coupling of a monolithic molecularly imprinted polymer to nano-liquid chromatography for the selective analysis of cocaine and its main metabolite, benzoylecgonine, in complex biological samples. After the screening of different synthesis conditions, a monolithic molecularly imprinted polymer was in situ synthesized into a 100 µm internal diameter fused-silica capillary using cocaine as template, methacrylic acid as functional monomer, and trimethylolpropane trimethacrylate as cross-linker. Scanning electron microscopy was used to assess the homogeneous morphology of the molecularly imprinted polymer and its permeability was measured. Its selectivity was evaluated by nanoliquid chromatography-ultraviolet, leading to imprinting factors of 3.2 ± 0.5 and 2.2 ± 0.3 for cocaine and benzoylecgonine, respectively, on polymers resulting from three independent syntheses, showing the high selectivity and the repeatability of the synthesis. After optimizing the extraction protocol to promote selectivity, the monolithic molecularly imprinted polymer was successfully on-line coupled with nano-liquid chromatographyultraviolet for the direct extraction and analysis of cocaine present in spiked human plasma and saliva samples. The repeatability of the obtained extraction recovery, between 85.4-98.7% for a plasma sample spiked at 100 ng.mL-1 , was high with relative standard deviation values lower than 5.8% for triplicate analyses on each of the three independently synthesized molecularly imprinted polymers. A linear calibration range was achieved between 100 and 2000 ng mL-1 (R 2 = 0.999). Limits of quantification of 14.5 ng mL-1 and 6.1 ng mL-1 were achieved in plasma and urine samples, respectively. The very clean-baseline of the resulting chromatogram illustrated the high selectivity brought by the monolithic molecularly imprinted polymer that allows the removal of a huge peak corresponding to the elution of interfering compounds and the easy determination of the target analyte in these complex biological samples.

Molecularly imprinted polymers are highly selective and cost-effective materials, which have attracted significant interest in various areas such as sample pretreatment and chromatographic and electrophoretic separations. This review aims to present the state of the art concerning the miniaturization of these materials in order to meet the societal demand for reliable, fast, cheap, and solvent/sample saving analyses. The polymerization route specificities for the production of miniaturized molecularly imprinted polymers in capillaries or chip channels, such as open tubular, packed particles, magnetic nanoparticles, and in situ imprinted monoliths, are investigated. Their performances as selective supports in solid phase extraction and as stationary phases in electrochromatography and liquid chromatography, as well as their possible perspectives are discussed.