Determination of dissolved silicon in natural water by inductively coulpled plasma-mass spectrometry after off-line preconcentration

A method based on Mg(OH)₂ coprecipitation followed by cation-exchange separation for the determination of dissolved silicon in natural waters by ICP-MS was developed. Studies on the parameters of coprecipitation indicate that dissolved Si could be quantitatively removed from solution by the formation of brucite Mg(OH)₂, initiated by the addition of NaOH. Separation of Si from Mg²⁺ was achieved using cation-exchange resin with 98% yields. The optimized procedure provides Si recoveries of various natural water samples are 99%-105%. The detection limit(3 s, n = 8) of dissolved Si is 4.5 μg/L. The reproducibility (n = 8) of the present study is less than 3 %.