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This paper reports an alternative analytical methodology for the determination of chloride and sulphate impurities in hexafluorosilicic acid, FSA, using capillary zone electrophoresis. The influence of different electrophoretic and matrix variables on electrophoretic response was studied. Samples were injected hydrodynamically onto a fused silica capillary of 63.5 cm  75 mm id, with an effective length of 55 cm. The capillary temperature was kept constant at 25 AE 1 C throughout the experiments. A voltage of À25 kV was applied (in anionic mode). The electrophoretic zones were detected with a fixedwavelength UV detector at 254 nm and a diode array detector at 254 and 370 nm. The final background electrolyte consisted of 20 mM sodium chromate at pH 8.0 containing 6% MeOH and 1.5 mM tetradecyltrimethylammonium hydroxide. In these electrophoretic conditions, the separation of chloride and sulphate anions is achieved in less than ten minutes. The introduction of a water gap before the sample injection increases considerably the capillary life. The electrophoretic method developed allows the determination of chloride and sulphate at mg L À1 concentration levels in industrial production FSA samples.

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Analytical chemistry offers useful tools to solve problems in industrial laboratories caused by traditional methods of analysis. A simple ion chromatographic method has been developed to determine chloride, bromide, nitrate, and sulfate in hexafluorosilicic acid and tetrafluoroboric acid. These materials contain high levels of fluorinated species at pH values lower than 1.0, which represent a challenging sample. Currently, these matrixes are analyzed by chemical methods with associated interferences. Optimization of the ion chromatography method was performed using industrial samples due to the absence of reference materials. In order to obtain the best chromatographic resolution, the sample dilution, flow rate, and eluent concentration were studied in an isocratic mode. The method was suitable for the separation of the anions in less than 30 minutes, without sample treatment other than dilution. Good linearity was obtained with correlation coefficients between 0.9951 and 0.9998. Limits of quantification were between 0.21 and 0.39 mg/L for chloride, bromide, nitrate, and sulfate in hexafluorosilicic acid and tetrafluoroboric acid, and the inter-and intra-day relative standard deviations were less than 15%.

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