Determination of gaseous sulphur dioxide by capillary isotachophoresis

An isotachophoretic method is described for the analysis of sulphur dioxide, a major contributor to air pollution and acid rain. Two different sampling procedures are presented: an absorbing bottle equipped with a fritted glass bubbler and a counter-current membrane collection chamber constructed from Kel-F. The sample is collected in a dilute solution of H2O2 and analysed as sulphate by capillary isotachophoresis (cITP). The limit of detection for the cITP method used was found to be 2.3 ppm. The range of sulphate concentrations analysed by cITP spanned 5-100 ppm; the gas flow-rates used for SO2 sampling varied from 170 to 660 ml/min. Good absorbing efficiency is observed for the absorbing bottle sampling system. Initial work on the membrane sampling system is also described. Under the conditions used in this initial study overall limits of detection were 1 ppm SO2 for the absorber bottles (with an 80 min sampling time) and 17 ppm for the membrane collection chamber. The method is low-cost, easily operated and needs no sample pre-treatment. (C) 1999 Elsevier Science B.V. All rights reserved.