Molecularly imprinted polymers (MIPs) are synthetic materials designed to have a predetermined selectivity for molecular targets. They are synthesized from self-assembled pre-polymerization complexes of functional monomers and a molecular template by either thermal- or photo-polymerisation, followed by template removal post MIP synthesis. The resulting polymer then possesses recognition sites complementary to the size, shape or/and functionality of the chemical or biological template (imprint) molecule. Selectivity mapping of the recognition sites in a MIP can then be performed in batch or dynamic binding experiments using the templates and template analogues with a non-imprinted polymer as control [1, 2]. This evaluation process is frequently limited by the availability of sufficient large sets of the template analogues, which must be chemically synthesised if they are not commercially available.

This investigation describes a comprehensive selectivity mapping procedure with polyphenol- and phytosterols-imprinted polymers using complex natural samples (grape seeds, grape marc extract and wine) as the test materials and capillary high-performance liquid chromatography (microHPLC) with electrospray ionization tandem mass spectrometry (ESI MS/MS) for the analysis. The information on the selectivity of the solid-phase extraction process was obtained through analysis of the binding behaviour of structural similar polyphenols/phytosterols and their identification by ion trap ESI MS/MS. The MIP solid-phase extraction protocols were then progressively refined until a high recovery of the target compounds was achieved from these complex samples.

These results confirm that this rapid and high-resolution method can be used for binding site characterisation, selectivity optimisation and monitoring of the performance of MIPs intended for solid-phase extraction of bioactive molecules and nutraceuticals from diverse agricultural waste streams.