Gas Chromatography of trimethylsilylated silicate anions

Abstract

The advantages of capillary-column gas chromatography (GC) in the analysis of trimethylsilylated silicate systems are demonstrated and separation parameters and measurement and calculation methods for the qualitative and quantitative analysis of different silicic acid solutions are outlined.

The problems of the trimethylsilylation procedures are discussed. Results obtained by GC after derivatization with bistrimethylsilylacetamide (BSA) as the trimethylsilylating agent indicate that both the unwanted condensation and hydrolysis during silylation are suppressed if the proton-trimethylsilyl is accelerated e.g., by a powerful trimethylsilyl donor such as BSA, and if the pH of the silylation reaction mixture is controlled.

Chromatograms of some silicic acid samples are compared with those of identical samples silylated according to Lentz and Götz-Masson, respectively. Comparison of both the qualitative and quantitative results indicates that the compositions of the original silicic acid solutions are best reflected in the chromatograms after silylation with BSA. The effect of the after-treatment of the silylated silicic acid solution with Amberlyst 15 cation-exchange resin is disscussed separately.