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

A flow-injection method has been developed for the determination of to tal sulphite in wine samples. After hydrolysis of bound sulphite, sulp hur dioxide is separated from the matrix by means of an in-line gas di ffusion module. For detection indirect amperometry is used, with iodin e as oxidizing reagent. The iodine can be generated in-line by merging and mixing iodate and iodide solutions, or alternatively, electrochem ically from iodide. With the latter method the best results were obtai ned. The reproducibility of the peak heights is better than 2%. The li near range of the method can be regulated by adaptation of the current applied to generate the iodine reagent. Due to the low detection limi ts 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 sulph ite concentration in different wine samples by titration.