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Free Sulfur Dioxide in Beer as the Difference between Total Sulfur Dioxide and Acetaldehyde: A Voltammetric Approach

2003; Taylor & Francis; Volume: 61; Issue: 4 Linguagem: Inglês

10.1094/asbcj-61-0191

1943-7854

Paulo Almeida, José A. Rodrigues, Luís F. Guido, João Rodrigo Santos, Aquiles A. Barros, Arnold G. Fogg,

Electrochemical sensors and biosensors

A method that involved voltammetric determination of the levels of total sulfur dioxide (SO2) and acetaldehyde was developed for the determination of the level of free SO2 in beer. Free SO2 concentration is calculated by the difference between the concentrations of SO2 (total) and acetaldehyde. In fact, it is shown that SO2 reacts almost completely with acetaldehyde, which represents more than 95% of all aldehydes present in beer. In a first step, aldehydes are removed from an alkalinized sample of beer with a stream of nitrogen gas, collected in an appropriate electrolyte trapping solution, derivatized with hydrazine, and determined by voltammetry at a hanging mercury drop electrode. The remaining beer solution is strongly acidified and purged with nitrogen. Total SO2 is collected in an appropriate electrolyte trapping solution and determined by voltammetry. The proposed method has a relative standard deviation of approximately 2.1 and 4.4% for total SO2 and free SO2 concentrations, respectively, normally found in beer. Results are in agreement with those obtained by the para-rosaniline reference method.