Anions in potable waters - Determination of Anions in Natural and Treated Waters - page 514

Fig. 7.12 Voltammogram of silicomolybdate at the HMDE in the presence of
methylethylketone, 0.2mol L −1 citrate buffer, pH 2,5 3×10 −7 mol L −1
SiO 2 , 10% ketone. MMDE surface area 2.8×10 −2 cm 2 , scan rate v
100mV s −1 , adsorption time t 120s at the starting potential E 2 —0.2V.
Curve 1—supporting electrolyte, curve 2-silico-molybdate
Source: Reproduced with permission from Marcel Dekker Inc [77]

Table 7.18 Determination of silica (SiO 2 ) in potable water

Nature of water
samples

Voltammetric method µg L −1
SiO 2

Spectrophotometric
method

Drinking water 1 140 130

2 150 155

3 190 180

4 110 130

5 130 140

Source: Reproduced with permission from Marcel Dekker Inc. [77]

Results obtained on applying the procedure to samples of potable water are summarised
in Table 7.18. For comparison the samples were analysed by the spectrophotometric
molybdenum blue method. The values obtained by voltammetry agree satisfactory with
this method, confirming the accuracy of the voltammetric determination.