Analysis of free and total sulfur dioxide in wine by using a gas-diffusion analytical system with pH detection.

The use of sulfur dioxide as preservative in winemaking industry has a direct impact on wine quality. The standard methods to analyze this parameter require several processes and are time consuming. In this paper a simple and rapid analytical method for free and total sulfur dioxide detection is proposed. This method is based on the separation of the analyte from the sample with a permeable gas diffusion membrane and its indirect detection with a pH sensor. The system has been validated and optimized for free sulfur dioxide detection in the range of 1-60mgL-1 and for total sulfur dioxide in the range of 30-300mgL-1 with a limit of detection of 0.5mgL-1. Validation of the system has been carried out using a total of 70 samples of white and red wines and two standard methods, the Ripper and the Paul method. The obtained values have demonstrated a good agreement for both methods.