Determination of trace anions in concentrated weak acids by ion chromatography

Ion-exclusion chromatography (ICE) followed by ion chromatography (IC) was used for the determination of trace anionic contaminants in concentrated we ak acids. The ICE separation was used as a pretreatment step to isolate the contaminant anions of strong acids from the excess of matrix ions. Then a fraction containing the analyte ions was separated using IC with suppressed conductivity detection. Microbore-ion-exchange columns were chosen to addr ess the increased purity requirements for use of these concentrated acids i n semiconductor applications. The chromatographic conditions were optimized for determining trace chloride, sulfate, phosphate, and nitrate in concent rated 24.5% (v/v) hydrofluoric acid; trace chloride, sulfate, and nitrate i n concentrated 85% (w/w) phosphoric acid and trace chloride and sulfate in concentrated 0.7% (v/v) glycolic acid. Method detection Limits for the anio ns of interest were below 100 mu g/l. (C) 1999 Elsevier Science B.V. All ri ghts reserved.