DETERMINATION OF SULFITE IN WINE BY FLOW-INJECTION ANALYSIS WITH INDIRECT ELECTROCHEMICAL DETECTION

A flow-injection method has been developed for the determination of total sulphite in wine samples. After hydrolysis of bound sulphite, sulphur dioxide is separated from the matrix by means of an in-line gas diffusion module. For detection indirect amperometry is used, with iodine as oxidizing reagent. The iodine can be generated in-line by merging and mixing iodate and iodide solutions, or alternatively, electrochemically from iodide. With the latter method the best results were obtained. The reproducibility of the peak heights is better than 2%. The linear range of the method can be regulated by adaptation of the current applied to generate the iodine reagent. Due to the low detection limits obtained (0.05 mg L-1), wine samples can be strongly diluted before injection, which makes the sample pretreatment fast and simple. Good agreement has been found with the results obtained for the total sulphite concentration in different wine samples by titration.