Evaluation of an HPLC method for the determination of sulphiting agents in foods

A method based upon a combination of a modified Monier-Williams procedure and an HPLC separation and quantitation of sulphite, has been developed. Its efficiency has been tested, in comparison with the Monier-Williams method, for the SO2 recovery in various foods. Desorption of SO2 from different matrices is obtained by distillation in strongly acid solution. Gaseous SO2, collected and oxidized to sulphate with hydrogen peroxide, is neutralized with sodium hydroxide. The neutralized solutions are diluted and injected by an autosampling injector into an HPLC apparatus consisting of a strong anion exchange column, eluted with a potassium hydrogen phthalate solution (0.15 g/l, pH 5.7) at a 3 ml/min flow rate and detected at 280 nm by an UV spectrophotometer. The combined method shows a good detection limit as well as high chromatographic resolution, avoiding potential interference of other volatile compounds. It is also time-saving and utilized basic laboratory equipment.