Flow Injection Analysis of Hydrogen Peroxide, Sulfite, Formaldehyde and Hydroxymethanesulfonic Acid in Precipitation Samples

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Abstract
Hydroxymethanesulfonic acid (HMSA), the reaction product of sulfite and formaldehyde plays an important part in the aqueous phase conversion of sulfite to sulfate. HMSA is fairly stable under acidic conditions and in presence of hydrogen peroxide. Sulfite is unstable under these conditions. A flow injection set-up was developed, which allows the determination of H2O2, sulfite, formaldehyde and hydroxymethanesulfonic acid. H2O2 analysis by amperometric detection offers the possibility of a simple, robust field instrument. The detection limit is 5μg/l and the method is linear up to 5mg/l. Based on the 4,4-dithiodipyridine/sulfite reaction selective and sensitive spectrophotometric detections were developed for sulfite, formaldehyde and hydroxymethanesulfonic acid. The detection limit of these compounds is 50μg/l and the method is linear up to 5mg/l. A large fraction of S(IV) is present as HMSA in fog, dew and precipitation samples in The Netherlands.