Determination of anionic impurities in hexafluorosilicic acid by capillary zone electrophoresis

Abstract

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.

Industrial Application of Ion Chromatography to the Quality Control of Fluorinated Inorganic Acids

“…The IC method also offers advantages compared to the capillary electrophoretic method previously applied to this matrixes (Ayarza et al 2012). The LOQs are lower than those obtained by CE, have higher sample throughput, and problems with capillary life are avoided.…”

“…A capillary zone electrophoresis method has been reported with an isotacophoresis initial step to determine anionic impurities on the silicon wafer surfaces treated with hydrofluoric acid vapor (Boden et al 1995). No references have been found dealing with the analysis of inorganic anionic impurities in fluorinated acids, apart from a previous study of our group (Ayarza et al 2012). In this previous study, the concentrations of chloride and sulfate were determined in hexafluorosilicic acid by capillary zone electrophoresis (CZE) with indirect photometric detection.…”

Recent Advances on Porous Siliceous Materials Derived from Waste

“…The type of feedstock and reactants used for the FSA production led to the formation of different secondary products that could persist as traces in FSA-derived SiO 2 . Ayarza et al [ 160 ] reported a new method for identifying impurities present in FSA implementing capillary zone electrophoresis, a method that could be applied at an industrial scale due to its simplicity and accuracy. In this study, the authors quantified as principal impurities the presence of chlorides and sulfates (both at a concentration of approx.…”