Characterization of silica dissolved in sodium chloride solution using fast atom bombardment mass spectrometry

The chemical species of silica dissolved in sodium chloride (NaCl) solution were identified by means of fast atom bombardment mass spectrometry (negative ion mode). The concentration of silica in 0.1 M NaCl solution is < 0.6 mmol dm(-3) (mM) and application to the identification of the silicate species at low concentrations such as in natural waters level is also possible. An apparent peak at m/z 95, which corresponds to SiO(OH)(3)(-) in 0.1 M NaCl solution, was not confirmed owing to the interference of the peaks corresponding to NaCl(2)(-); however, peaks for complexes such as Si(OH)(2)O(2)Na(-), Si(2)(OH)(5)O(2)(-), Si(2)(OH)(4)O(3)Na(-), Si(2)(OH)(3)O(4)Na(2)(-), Si(2)(OH)(2)O(5)Na(3)(-), Si(4)(OH)(7)O(5)(-), Si(4)(OH)(6)O(6)Na(-) and Si(4)(OH)(5)O(7)Na(2)(-) were detected. The existence of the trimer and its Na(+) complexes such as Si(3)(OH)(7)O(3)(-), Si(3)(OH)(6)O(4)Na(-) and Si(3)(OH)(5)O(5)Na(2)(-) was not clearly shown. These complexes can be confirmed not only in the form of the anion itself (e.g. Si(2)(OH)(5)O(2)(-)), but also in the form of some complexes with sodium ions, such as Si(2)(OH)(4)O(2)Na(-). Copyright 2000 John Wiley & Sons, Ltd.