Exploring the versatility of capillary electrophoresis for the analysis of ionic species in vehicular emission

In this work, the condensed aqueous-phase vapor of vehicle exhausts was collected in a controlled manner and its major ionic components were determined by capillary electrophoresis with indirect UV-detection. Giving the complexity of the sample, a systematic procedure for optimization and method development, previously implemented in our laboratory, was performed. The electrolytes 3,5-dinitrobenzoic (pH 5) and chromate (pH 8.5), containing cetyltrimethylammonium bromide (CTAB) as flow modifier, were used to analyze organic and inorganic anions, respectively. Among the organic anions, it was found formate, acetate, pyruvate and lactate. Among the inorganic anions, chloride, sulfate, nitrite, nitrate and carbonate were the most abundant. Cations were analyzed in imidazole (pH 4.5), containing hydroxy-isobutyric acid and bicyclohexane 18-crown-6 ether as modifiers. Samples originated from the pipe tail exhaust of vehicles that support catalytic converters as part of their emission control system, presented a much smaller concentration of organic anions and a larger concentration of carbonate ion, confirming that the combustion in these vehicles is far more complete. It was evidenced in all studied samples, the presence of ammonium ion, suggesting an in situ reduction of nitrogen to ammonia. (C) 1999 Elsevier Science B.V. All rights reserved.