Determination of organic acids in air by capillary electrophoresis and ion-exclusion chromatography

A capillary electrophoretic (CE) method for the determination of organic ac ids in the low ppm range is described. The buffer consisted of 5 mM 2,6-pyr idine-dicarboxylic acid and 0.5 mM cetyltrimethylammonium bromide, pH 5.6. The former served as background electrolyte for indirect UV detection at 20 0 nm, whereas the latter was used to reverse electroosmotic flow. In < 5 mi n 8 low molecular mass organic acids (oxalic, formic, malonic, glutaric, gl ycolic, acetic, lactic and propanoic) and two inorganic acids (hydrochloric and sulphuric) were separated. Detection limits for anions tested were 0.0 4 mg L-1 (lactic acid) to 0.6 mg L-1 (malonic acid). The method was applied to the determination of organic acids in air samples . The CE results when compared with ion-exclusion chromatography (IEC) agre ed well. The use of electrokinetic injection in CE proved beneficial for pr econcentration of organic acids in real samples. Using electrokinetic injec tion, preconcentration factors ranging from 14 (hydrochloric acid) to 3 (pr opanoic acid) were obtained.