ABSTRACT

Sulfur dioxide, in an ambient air sample, is collected in a buffered formaldehyde absorber solution, which enhances the collection efficiency and stabilizes the resulting sulfite from oxidative loss. Potassium hydrogen phthalate is used as the buffer in the absorber and formaldehyde as the stabilizer for the sulfite species, which forms the oxidation resistant species, hydroxymethanesulfonate (1),(2). The procedure is similar to method 704A in absorption and recovery efficiency, sensitivity and precision, and avoids the use of the toxic and costly tetrachloromercurate (II). In addition, stability of the collected SO2 is greatly enhanced over method 704A. The analytical measurement is based on the formation of the intensely colored pararosanilinemethylsulfonic acid which is produced from sulfite, pararosaniline and formaldehyde.