Determination of silicate, simultaneously with other nutrients (nitrite, nitrate and phosphate), in river waters by capillary electrophoresis Original Research Article

Capillary electrophoresis with an indirect UV detection was used in this study to analyse silicate, simultaneously with other nutrients (nitrite, nitrate, phosphate). The separation was achieved in a fused silica capillary filled with an electrolyte solution containing sodium chromate and an electroosmotic flow modifier, trimethyltetradecylammonium bromure (TTAB). The effect of the TTAB concentration and electrolyte solution pH on the electrophoretic mobility of the species is being discussed. The best simultaneous separation of these species is achieved with 0.2 mM TTAB and an electrolyte pH of 11 within 10 min. Detection limits were 0.73, 1.13, 0.60 and 1.32 μM for nitrite, nitrate, phosphate and silicate, respectively. Reproducibility is below 10% whatever the species. This method was applied to determine these species in different samples of river water and the results were compared with those of conventional colorimetric method measurements. The two methods do not give significantly different values for the mean concentration of these anions.