Ion chromatographic determination of atmospheric sulfur dioxide and ammonia collected with sodium carbonate- and phosphoric acid-impregnated filters

Sodium carbonate- and phosphoric acid-impregnated filters were tested for use in selective collection of SO₂ and NH₃ in the atmosphere. Collection efficiencies of SO₂ and NH₃ with these impregnated filters were measured by SO₂ and NH₃ standard gases at the levels below ppm. The collection efficiency of SO₂ with Na₂CO₃ impregnated filter was higher than 96% at both high(~80%) and low(~10%) humidity, and the filter did not catch NH₃. Therefore, it was concluded that the Na₂CO₃ impregnated filter had a good selectivity for SO₂ and NH₃ collection. Although the H₃PO₄-impregnated filter substantially collected SO₂, especially at high humidity, it showed the sufficient collection efficiency for NH₃. Air samples should be first passed through the Na₂CO₃-impregnated filter, then through the H₃PO₄-impregnated filter. Both Na₂CO₃- and H₃PO₄-impregnated filters collected SO₂ and NH₃, were separately extracted with distilled water and subjected to ion chromatography. Sulfur dioxide being equivalent to the sulfite in the extracting solution was oxidized to sulfate with H₂O₂, and determined as sulfate. The detection limit in this method was 2 ppb for SO₂ and NH₃ when 0.3 m₃ of air was sampled.