Exploiting Sulphide Generation and Gas Diffusion Separation in a Flow System for Indirect Sulphite Determination in Wines and Fruit Juices

Abstract

A flow system for sulphite determination in wines and fruit juice samples has been developed exploiting H2S generation and gas diffusion separation. The composed sandwich gas diffusion cell was coupled in the flow manifold to permit sulphite reduction to H2S and H2S diffusion through a microporous PTFE membrane to produce methylene blue resulting from the reaction with N,N-dimethylphenylene diamine (DMPD) and Fe3+. The flow parameters were optimized, and the best results were obtained by using NaOH solution for H2S collection. Interferences of H2S, CO2 and ascorbic acid were evaluated. Limits of detection (3σ) for the free and total sulfite were calculated at 0.12 and 0.25 mg L−1, respectively. The results obtained by the proposed process were in agreement with the reference methods for a 95% confidence level.