SEPARATION OF INORGANIC AND ORGANIC ANIONIC COMPONENTS OF BAYER LIQUOR BY CAPILLARY ZONE ELECTROPHORESIS .1. OPTIMIZATION OF RESOLUTION WITH ELECTROLYTE-CONTAINING SURFACTANT MIXTURES

The simultaneous separation of chloride, sulfate, oxalate, malonate, fluoride, formate, phosphate, carbonate and acetate in Bayer liquor using capillary zone electrophoresis with indirect detection is demonstrated using electrolytes comprising binary mixtures of the surfactants tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DTAB). Two optimal electrolyte compositions were identified, namely 3 mM TTAB, 3 mM DTAB and 7.5 mM chromate at pH 9 (optimum 1) and 5 mM TTAB, 1 mM DTAB and 5.5 mM chromate at pH 9 (optimum 2). The separation selectivities of these electrolytes differ and the choice between them rests on consideration of the relative concentrations of the ionic species in the sample. Best results were obtained when the Bayer liquor sample was diluted by a factor of 500 before analysis. Linear calibrations were achieved in the working concentration range (1-10 mu g/ml) and detection limits fell in the range 0.09-0.34 mu g/ml for optimum 1 and 0.16-0.88 mu g/ml for optimum 2. Recoveries of ions added to the diluted sample were close to quantitative, except for phosphate which showed low and variable recovery, and carbonate which was also variable due to absorption of carbon dioxide by the sample. Tartrate and succinate could not be resolved with either of the optimal electrolyte compositions.