Determination of Silicate by Capillary Electrophoresis with Contactless Conductivity Detection

A new method for the rapid separation and sensitive determination of silicate in drinking natural mineral water by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C(4)D) was developed. The analyte could be separated well within 6 min in a fused-silica capillary under the optimum conditions: 2.4 mmol/L KOH + 1. 6 mmol/L K(2)HPO(4) + 0.4 mmol/L CTMAB as the running buffer, CTMAB as the electroosmotic flow modificator, negative polarity separation voltage, - 15 kV. The linear response ranged from 2.0 mg/L to 80 mg/L with the LOD= 0.5 mg/L. The relative standard deviations of the intra- and inter-day precision were 3.5% and 3.8%, respectively. The effects of the component of the running buffer, the interference of PO(4)(3-) and colorants in samples were discussed. Contents of silicate in drinking natural mineral water samples could be easily determined by the proposed method with satisfactory results. It was free from phosphate and colorants interference.