Multivariate design and application of novel molecularly imprinted polymers selective for triazole fungicides in juice and water samples

Abstract

In the present study, novel molecularly imprinted polymers were prepared using penconazole as template and different combinations of functional monomers (acrylic acid (AA) and N-isopropylacrylamide (NIPAM)) and cross-linkers (ethylene glycol dimethacrylate (EGDMA) and trimethylolpropane trimethacrylate (TRIM)), according to a Plackett-Burman design of experiments. Materials were fully characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and nitrogen adsorption analysis. Rebinding behaviors in solution were studied both at the equilibrium (Langmuir, Freundlich and Temkin models), and at the non-equilibrium (pseudo-first, pseudo-second order kinetics). Materials were further tested as sorbents for dispersive solid phase extraction (d-SPE) on apple juice for multicomponent recovery of triazole fungicides at trace level, testing several variations of extraction parameters (juice pH, amount of sorbent, adsorption time, desorption solvent, desorption time) leading to the selection of the best materials and simultaneously of the best extraction conditions. MIPs synthesized with NIPAM showed significatively higher affinity for triazole pesticides in apple juice than the ones synthesized with AA, while no differences emerged for the two cross-linkers employed (EGDMA, TRIM). Selectivity was also assessed, testing MIPs as d-SPE sorbents in undiluted apple juice spiked with triazole pesticides concurrently with other interfering compounds. The newly developed NIPAM-based penconazole-imprinted MIPs showed an excellent recognition mechanism towards compounds containing the triazole ring, and significatively lower recoveries for other compounds. The developed analytical procedure based on molecularly imprinted polymer dispersive solid phase extraction and liquid chromatography coupled with mass spectrometry (MIP-d-SPE-LC-MS) was validated for selective enrichment and determination of triazole compounds in apple juice samples and river water samples with good recoveries (94.67%–109.03% for river water, 89.79%–110.23%, for apple juice), high repeatability (RSD% < 3.97 for river water, RSD% < 4.85 for apple juice), and reproducibility (RSD% < 5.95 for river water and RSD% < 7.14 for apple juice).