Multivariate Optimization of Voltammetric Parameters for the Determination of Total Polyphenolic Content in Wine Samples Using an Immobilized Biosensor

This work was aimed at investigating the changes in the determination of total phenolic (TP) content in wine samples using catechin as a standard. The modification of the glassy carbon electrode (GCE) was carried out using green apple as an enzymatic source of polyphenol oxidase. The experimental variables were optimized using the Box-Behnken design with 3 factors in 15 runs of differential pulse voltammetry (DPV). The design was run in a single block fashion while the order of the experiments was fully randomized to provide greater protection against the effects of lurking variables. Specifically, the three optimized factors included the buffer pH, deposition time (t(d)) and scan rate (s(r)). Based on the optimized results obtained, we selected the most suitable condition for the determination of the TP content in wine samples as follows: phosphate buffer of pH 7.65 as supporting electrolyte, td 29.8 s and s(r) 25.0 mV/s respectively. The method was optimized with respect to the current signal at a deposition potential of 0.2 V and within an oxidation potential of -0.2 V to 0.6 V. Good analytical responses were obtained with apple sensors for the detection of TP in wine samples, with a higher concentration in red wines than in white wines.