Development of a molecularly imprinted polymer for patulin in apple juice

The design of imprinted polymers selective towards patulin (PAT) and their application in food analysis are reported for the first time. Different templates, functional monomers and molar ratios were evaluated related to binding capacity and specificity. Besides the toxin itself, the implementation of structural analogues (2-hydroxynicotinic acid, 5-indanol and 3-hydroxyphtalic anhydride) as templates was evaluated. A molecularly imprinted solid-phase extraction (MISPE) procedure was optimised for the selective clean-up of apple juice samples. Depending on the spiked concentration, recoveries after MISPE and non-imprinted solid-phase extraction varied respectively from 60% to 66% and from 40% to 41%. Limit of detection and limit of quantification were 10.0 mu g/kg and 33.3 mu g/kg, respectively. Equilibrium experiments and Scatchard analysis disclosed the presence of two classes of binding sites in the imprinted polymer. The dissociation constant (K-D) of the higher affinity binding sites was 3.3 mu mol/l, while the K-D of the lower affinity binding sites was 260.7 mu mol/l. The performance of the molecularly imprinted polymer throughout the clean-up was compared to liquid-liquid extraction and a C-18 sorbent. Cross-reactivity experiments demonstrated that MISPE was substantially more selective than C-18 clean-up. Moreover chromatograms, with less interfering peaks, were observed with MISPE resulting in a sensitive and reliable quantification of PAT.