Determination of sulfites in foods by simultaneous nitrogen purging and differential pulse polarography

An improved technique has been developed for determination of sulfites in food by differential pulse polarography. A Teflon sleeve is fitted to the dropping mercury electrode capillary so that SO2 is purged from the sample and simultaneously detected at peak potential. Bound sulfite in the sample is released at room temperature by addition of base in the absence of oxygen. For some foods, the prepared sample was passed through a Sep-Pak C-18 cartridge to remove naturally occurring sulfur compounds so that only added sulfite is measured. The level of detection was approximately 1 microgram SO2/g. Results agreed with those obtained by the optimized Monier-Williams method for a variety of foods.