Using of molecularly imprinted polymers for determination of gallic and protocatechuic acids in red wines by high performance liquid chromatography

Abstract

The sorption capacities of gallic- and protocatechuic acid-molecularly imprinted polymers (GA-MIP and PCA-MIP, respectively) and non-imprinted polymer (NIP) have been determined on the piston columns by the frontal analyses (FAs). Mobile phases consisted of MeOH, MeOH/H2O (1:1), 12.5% EtOH or ACN. Solutes concentrations used in FAs were 1μg/mL and 50μg/mL. All sorption capacities were depended on analyte and solvent used. Results obtained from the FAs have shown that both imprinted polymers almost always were preferentially recognized PCA molecule. Only in MeOH, the GA-MIP had ability to recognize its template molecule positively. Surprisingly, in some cases, also the NIP exhibited higher sorption capacities than the MIPs for their templates, e.g. in ACN for GA or in MeOH for PCA. This behaviour indicates that in some solvents, the low affinity sites of the blank polymer can act as strong interacting sites. In the next, prepared MIPs were successfully used as the SPE-sorbents for the extraction and purification of chosen phenolic acids from red wine samples. The recoveries both of MIPs were the highest for PCA, what was in agreement with the experiments carried out in 12.5% EtOH during FAs. Prepared MIP-beads allowed the purification of chosen red wine samples with satisfactory selectivities and high recoveries. The linearity of the method was in the range from 10μg/mL to 70μg/mL and 0.1μg/mL to 4.5μg/mL for GA and PCA, respectively, with the determination coefficients ranging from 0.996–0.999. The LODs (S/N=3) ranged from 0.1μg/mL to 0.4μg/mL. The RSDs for the recoveries varied from 4.0% to 8.1%. The PAs-MIPs and corresponding NIP were also characterized by attenuated total reflectance analysis Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron analysis (SEM).