Potentiometric Quantification of the Benzoate Ion in Nonalcoholic Beverages Using a Solid Electrode Modified with a Polypyrrole-Based Selective Membrane

This work presents the results obtained on the construction of a potentiometric ion‐selective electrode based on a polypyrrole (PPy) selective membrane to quantify the benzoate ion in nonalcoholic beverages. The electrode modification with benzoate (Benz−1) ion doped‐Ppy was carried out under an imposed potential, while the electrosynthesis optimization was undertaken using the modified Simplex method, such that the film’s sensitivity was maximized toward the benzoate ion. The maximum sensitivity recorded was −52.02±1.55 mV/decade [Benz−1] using a graphite powder‐araldite resin composite electrode. During the modified electrode’s characterization it was found out that the response and drift were relatively short, namely 2 min and 0.4 mV min−1 respectively, within the 7 to 9 pH range, exhibiting a detection limit of 7×10−4 mol L−1 and a quantification range of 3×10−3 at 10−1 mol L−1. Selectivity coefficients were evaluated with the Matched Potential Method obtaining in all cases values much less than 1. The benzoate concentration in commercially available juices and sweetened beverages was evaluated comparing the results obtained with the proposed ion‐selective electrode and those of HPLC, the usually accepted technique. A statistical analysis of the results led to the conclusion that there exists no meaningful difference between the results obtained with both techniques, which shows the usefulness of the ion‐selective electrode to proceed with the quantification in real samples.