A simple method for the direct determination of silica in drinking, sea and boiler water was developed. It is based on interfacial preconcentration of silicomolybdate at the electrode (HMDE) and subsequent voltammetric determination. Silica reacts with molybdate at pH 1.6 ± 0.1 to form silico molybdate. By addition of methylethylketone silicomolybdate is completely converted to the β-form. Citrate addition masks any phosphate, if present, and also excess of molybdate. By keeping the initial potential of the HMDE at −0.2 V for 2 min the silicomolybdate is accumulated by adsorption in the interface. Then its bulk concentration is determined by measuring the peak height at −0.36 V. Traces of silica in drinking, sea and boiler water are determinable down to 1 × 10−7M or 6.4μg/l SiO2.
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Iyer et al. (1981) studied this question.
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