SULFITE OXIDATION AT A PLATINUM GLASSY-CARBON ELECTRODE - DETERMINATION OF SULFITE BY ION-EXCLUSION CHROMATOGRAPHY WITH AMPEROMETRIC DETECTION

The electrocatalytic oxidation of sulfite in an acidic medium at a platinum-based, chemically modified glassy carbon electrode (Pt-CME) was investigated. The electrode was characterized by voltammetry and flow injection, and applied to the determination of total and free sulfite by ion-exclusion chromatography with direct current and pulsed amperometric detection. The described electrode showed a promising combination of background current stability, catalytic activity detection limit (0.25 and 0.50 mu g l(-1) by direct current and pulsed amperometric detection, respectively) and reproducibility. Examples of determination of free and total sulfite present in fruit juice were achieved by ion chromatography with electrochemical detection. The detector can be used for the analysis of real samples, avoiding tedious or complex pretreatment, with an acceptable level of selectivity and accuracy.