SPECIFIC DETERMINATION OF AEROSOL SULFURIC-ACID IN THE PRESENCE OF AMMONIUM-SULFATE - LABORATORY STUDY

A method has been developed to specifically determine H2SO4 aerosol in the presence of other particulate sulfates, including (NH4)2SO4. Prior to collection, the sample stream is heated to reduce relative humidity to ~40% such that (NH4)2SO4 as well as other particulate sulfates are collected as solid particulates and do not react with the collection filter impregnating reagent. The glass fiber collection filter is impregnated with 2-perimidinylammonium bromide and collected H2SO4 is immobilized as the sulfate salt. The collected particulate sulfates are converted to BaSO4 by treatment with a barium acetate solution in methanol-acetone. Excess impregnating reagent is removed by frontal elution chromatography with methanol and then the organic sulfate is converted into an intensely colored compound, 2-amino, 4,6,9-trinitroperimidine, by reaction with HNO3. This compound behaves as an indicator and after adding excess base the intensity of the developed color is measured at 550 nm. The sensitivity of the method is 0.1 μg H2SO4 and the working range is 0.2-50 μg H2SO4. © 1979.