1991 Volume 40 Issue 8 Pages 425-428
A new FIA system was developed for the continuous determination of total silica in natural water. The system includes the conversion of polymerized silica into its monomer. A sample (20μI) sandwiched between two 100 μl layers of alkaline reagent is introduced into a stream of distilled water at a flow rate of 1.3 ml/min. The polymerized silica in the sample is decomposed to monomer in 10 m Teflon tubing heated in an air bath at 145°C. The sample is merged with a stream of acidic molybdate reagent at a flow rate of 0.6 ml/min, and then is heated at 90°C to produce yellow molybdosilicate. The absorbance of the yellow complex is measured at 400 nm. The silica, ranging from 0.5 to 100 mgSi/l, could be determined at a sampling rate of 30 samples/h. The precision of the method is 1.5% (RSD) for 50 mgSi/l. The flow injection method proposed here was applied to the quantitative analyses of total silica in several geothermal water and colloidal silica samples. The results obtained by the proposed FIA were in good agreement with those obtained by the conventional method (PS K 0101).
