Potential interferences in the anhydrous isopropanol (a‐IPA) extraction method for separating sulfuric acid from particulate sulfate on filters were investigated. The method involves separation and recovery of the acid with a‐IPA, followed by aqueous extraction of the particulate sulfate. Analysis for sulfate in the two separate fractions was performed by ion chromatography. The solubility of ammonium sulfate in a‐IPA was measured and the effects of temperature and moisture content of the solvent on ammonium sulfate solubility were determined.