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.

Keywords:

• conductometry
• multipumping flow system
• sulfites
• sulfur dioxide (SO2)
• wine

Additional information

Funding

This work has been funded by the Spanish Ministry of Economy and Competitiveness (MINECO project CTQ2016-77155-R) and by FEDER. Kaewta Danchana. acknowledges the financial support from the Conselleria d’Innovació, Recerca I Turisme of the Govern de les Illes Balears and of the Fons Social Europea (FPI/1867/2016). S. Clavijo acknowledges to the Torres Quevedo Program of the MINECO co-financed with European Funds for the financial support through the PTQ-2015-08038.