Simultaneous determination of silicic acid, Ca, Mg and Al in mineral water and composite tablets by ion chromatography

A simple, selective and sensitive ion-chromatography method was investigated for simultaneously determining silicic acid, Ca2+, Mg2+, Al3+ and anions (Cl- and NO3-) in real samples. it involved a single-column ion-chromatograph with sodium hydroxide-methanol-water eluent and conductometric detection. Cations were converted to complex onions ky adding EDTA to the sample solution. A set of well-defined peaks of silicic acid, Ca2+, Mg2+, Al3+, Cl- and NO3- were obtained. Detection limits using 3.3 sigma (sigma = standard deviation of blank solution) were 1.25 x 10(-6) M for H3SiO4-, 1.32 x 10(-6) M for Ca2+, 1.28 x 10(-6) M for Mg2+, 1.33 x 10(-) (6) M for Al3+, 1.31 x 10(-6) M for Cl- and 1.24 x 10(-6) M for NO3-. The method was successfully applied to analysis of mineral water and composite tablets.