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Most pollutant compounds exist as mixtures in the environment. In this regard, one of the 12 principles of green analytical chemistry emphasizes the need for methods that allow for analysis of multiple compounds versus those that analyze a single analyte at a time. In this work, we present a molecularly imprinted polymer (MIP) synthesized for the selective and efficient extraction of selected pharmaceuticals belonging to five different classes, namely an antiretroviral (nevirapine), an antidepressant (venlafaxine), a muscle relaxant (methocarbamol), an anticonvulsant (carbamazepine) and a cardiac stimulant (etilefrine) from surface water samples. Cavity tuning experiments using the target pharmaceuticals as a single or multi-template were conducted and the venlafaxine-imprinted polymer was successfully selected for the study based on its high selectivity toward targeted pharmaceuticals. Batch adsorption and kinetic studies showed that adsorption of the selected pharmaceuticals onto the particles of the polymer followed a Freundlich adsorption isotherm as well as a pseudo-second-order adsorption model. This indicated heterogeneity of the binding surface energies on the MIP resulting in multiple interactions through chemisorption. An analytical method for quantification of the compounds using liquid chromatography-mass spectrometry (LC–MS) was successfully developed, with detection limits ranging from 0.03 to 0.31 ng mL−1 and quantification limits in the 0.12–3.81 ng mL−1 range. The imprinted polymer was then evaluated as a selective adsorption sorbent for solid-phase extraction (SPE) of the selected pharmaceuticals in dam water samples followed by LC–MS analysis, giving recoveries ranging from 43 to 69%.

In this work, we demonstrate the development, evaluation and pre-liminary application of a novel passive sampler for monitoring of selected pharmaceuticals in environmental waters. The samplers were calibrated in laboratory-based experiments to obtain sampling rates (Rs) for carbamazepine, methocarbamol, etilefrine, venlafaxine and nevirapine. Passive sampling was based on the diffusion of the target pharmaceuticals from surface water through a membrane bag which housed an ionic liquid as a green receiving solvent and a molecularly imprinted polymer. Effects of biofouling, deployment time and solvent type for the receiver phase were optimized for selective uptake of analytes in surface water. Notably, there was a decrease in the uptake of selected pharmaceuticals and consequently a decrease in their sampling rates in the presence of biofouling. The optimum matrix-matched sampling rates ranged from 0.0007 - 0.0018 L d

This work demonstrates development and evaluation of a two-way technique based on the combination of membrane assisted solvent extraction and a molecularly imprinted polymer (MASE-MIP) for selective and efficient extraction of five selected pharmaceuticals belonging to five different therapeutic classes. The pharmaceuticals were extracted from surface water samples followed by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-qTOF/MS) determination. A central composite design was applied to optimize the influence of the sample salt content, the stirring rate, the stirring time and the amount of MIP on the extraction of an anticonvulsant (carbamazepine), a cardiac stimulant (etilefrine), a muscle relaxant (methocarbamol), an antiretroviral (nevirapine) and an antidepressant (venlafaxine) from surface water. Optimization of the analytical method was performed by spiking water with a mixture of all five pharmaceuticals at 500 ng mL−1. Optimum extraction conditions for a sample volume of 18 mL were found to be 5 g of salt content, a stirring rate of 400 rpm, an extraction time of 60 min and 50 mg of MIP. The MASE-MIP-LC-qTOF/MS method gave detection and quantification limits ranging from 0.09 to 0.20 ng mL−1 and 0.31–0.69 ng mL−1, respectively. The spiked river water samples yielded recoveries ranging from 38 to 91% for the selected model compounds belonging to the five classes of pharmaceuticals. Upon the application of the developed analytical method in water analysis, all selected pharmaceuticals were detected in South African river water with nevirapine and venlafaxine being more prominent attaining the maximum concentrations of 1.64 and 2.48 ng mL−1, respectively.