ANALYSIS OF OXALATE IN BAYER LIQUORS - A COMPARISON OF ION CHROMATOGRAPHY AND CAPILLARY ELECTROPHORESIS

The performances of ion chromatography (IC) and capillary electrophoresis (CE) are compared for the quantitative analysis of oxalate in Bayer liquor, an industrial process solution used in the extraction and precipitation of alumina from bauxite. CE has a number of advantages over IC for this particular application. The most important difference between the two techniques was the fact that the selectivity of CE allowed for complete resolution of oxalate from the matrix components in Bayer liquor. However, oxalate results obtained by IC were consistently higher than those for CE due to the presence of chromatographic interferences. Chloride and sulfate could also be determined with oxalate in the same separation using CE, however the simultaneous determination of oxalate, chloride and sulfate in Bayer liquors was not possible by IC due to significant chromatographic interferences. CE gave improved precision for the replicate analysis of oxalate in liquor samples, with an overall average of 1.71% R.S.D., compared to an average of 2.85% R.S.D. when using IC. A further advantage of CE was the fact that it also allowed the simultaneous determination of oxalate, chloride and sulfate in liquor samples which had been stabilised with tartaric acid.