P. Dasgupta, K. DeCesare, J. C. Ullrey
Oct 1, 1980
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1
Influential Citations
149
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Journal
Analytical Chemistry
Abstract
Formaldehyde (7 mM) buffered at pH approx. 4 is used to stabilize atmospheric SO/sub 2/ as hydroxymethanesulfonic acid. Equilbrium data for the above reaction are presented. Sulfite, liberated from the compound by base, is added to acidic pararosaniline for color development by the Schiff reaction, and absorbance is measured at 580 nm. The procedure has been optimized with regard to acidity and reagent concentrations. The method is comparable to the West-Gaeke method in absorption and recovery efficiency, sensitivity, and precision. No unusual interferences are observed due to O/sub 3/, NO/sub 2/, and transition-metal ions, except Mn(II). A novel ion chromatographic procedure to determine hydroxymethanesulfonate and sulfate in the same sample is also described. Enhancement of sensitivity in the colorimetric method by solvent extraction has been studied. Investigations into the mechanism of the Schiff reaction and structure of the products have established the validity of the alkylsulfonic acid theory. Mechanistically an aminocarbinol seems to be the first intermediate, which undergoes subsequent nucleophillic substitution by bisulfite ion. To account for the high absorptivity of the product, we suggest that the sulfonic acid group is significantly ionized.