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.
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