GAS-DIFFUSION FLOW-INJECTION ANALYSIS TO THE DETERMINATION OF SULFITEAND SULFUR-DIOXIDE IN ENVIRONMENTAL-SAMPLES

Flow injection analysis procedures utilizing gas diffusion separation (GD-FIA) have been developed for the spectrophotometric determination of free and formaldehyde-bound sulfite. Using 4,4'-dithiodipyridine as colorimetric reagent sulfite in tile concentration range 0.25-20 mg l (-1) can be determined with high precision and reliability. Excellent selectivity is achieved through the membrane separation step - high le vels of nitrite, sulfide and cyanide being the only interferents. A th orough investigation on the release of SO2 from sulfite solutions stab ilized with various agents has been conducted. The results of this stu dy evidenced the necessity of careful consideration of the experimenta l conditions in the donor stream and proper choice of standard solutio ns for calibration. The application of the proposed method to the anal ysis of water water revealed high recovery rates for added sulfite. De termination of atmospheric SO2 following liquid-trapping in buffered f ormaldehyde solution showed reasonable agreement with results obtained by standard reference methods.