Conductometric Determination of Sulfur Dioxide in Wine Using a Multipumping System Coupled to a Gas-Diffusion cell

Abstract

A conductometric system with a multipumping module and a gas-diffusion cell has been developed to determine free and total sulfur dioxide (SO2) in wine. The developed method has two protocols to determine both types of SO2 using the same system. For free SO2, sulfite is converted to H2SO4 by acidification and diffusion with H2O2 in an acceptor channel. The sample was previously hydrolyzed by mixing the sample with NaOH and heated at 70 °C prior making the determination of total SO2 in order to break the bonds of the combined SO2. Free and total SO2 were determined in the ranges of 2.5–25.4 and 10.2–76.2 mg L−1 with a sample throughput of 13 and 12 h−1, respectively. The calibration curves of free and total SO2 were in the range of ΔG (mS cm−1) = (–1.0242 ± 0.2871) + (0.6613 ± 0.0201) [SO2, mg L−1], r2 of 0.997 and ΔG (mS cm−1) = (–0.5850 ± 0.1678) + (0.1236 ± 0.0033) [SO2, mg L−1], r2 of 0.997. The proposed automated method is simple and easy to apply for the determination of SO2 in wine using simple reagents.