Anodic oxidation of parabens in acetic acid–acetonitrile solutions

The electrochemical properties of esters of p-hydroxybenzoic acid, called parabens, were investigated on a carbon fiber microelectrode and on a glassy carbon macroelectrode in glacial acetic acid containing 20 % acetonitrile (v/v) and sodium acetate as a supporting electrolyte. The anodic oxidation of parabens in this medium proceeds in a single stage giving well-shaped peaks or waves in the same potential region of above 1.0 V (vs. Ag/AgCl). The electrode process was characterized as being quasireversible, diffusion-controlled, and proceeds with the exchange of one electron and one proton. Phenoxyl radicals as products of the electrode process are chemically unstable and participate in the successive irreversible homogenous reactions resulting in electroinactive products (EqCi mechanism). Smaller oxidation potentials for parabens in comparison to such unsaturated fatty acids as oleic, linoleic, and linolenic ones indicate that these compounds can show antioxidative properties. Since parabens are often used as preservatives in many products, the results presented can be found useful in the determination of their total content in real samples.