Chemical Derivatization in Gas Chromatography

Mit Hilfe papierchromatographischer, kinetischer und rontgenographischer Methoden wird gezeigt, das das Tetramethylammoniumsilicat der Zusammensetzung 1 N(CH3)4OH · 1 SiO2 · ∼8 H2O nicht – wie bisher angenommen – ein Poly- oder Phyllosilicat, sondern ein Tetra-anhydrido-bis-cyclotetrasilicat (Doppelviererringsilicat) der Formel [(CH3)4N]8[Si8O20] · ∼69 H2O ist. Durch Umsatz mit Hexamethyldisiloxan wurde daraus der entsprechende Trimethylsilylester ((CH3)3Si)8[Si8O20] in kristallisierter Form erhalten.



By means of paperchromatographic, kinetic and X-ray methods it is shown that the tetramethylammonium silicate of the composition 1 N(CH3)4OH · 1 SiO2 · ∼8 H2O has not – as hitherto supposed – the constitution of a poly- or phyllosilicate, but that of a tetra-anhydrido-bis-cyclotetrasilicate (double-fourringsilicate), [(CH3)4N]8[Si8O20] · ∼69 H2O. Its trimethylsilylation by means of hexamethyldisiloxane gives the corresponding, crystalline trimethylsilyl ester [(CH3)3Si]8[Si8O20], which has been characterised by mass spectroscopy.

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Die Konstitution des Tetramethylammoniumsilicats der Zusammensetzung 1,0 N(CH3)4OH 1,0 SiO2 · 8,0–8,3 H2O

Gas chromatography and mass spectrometry of the trimethylsilyl derivatives of inorganic anions

A fundamental understanding of aqueous silicate chemistry is a prerequisite to unraveling silicon's (Si) role in living systems. Owing primarily to the advent of 29Si nuclear magnetic resonance (NMR) spectroscopy, the depth of that understanding has increased dramatically over the past two decades. By comparison, details of the biochemistry of Si are sparse. Although several proteins and amino acids believed to be associated with silicates have been isolated, no organosilicon compounds have so far been identified under physiological conditions. Nevertheless, hypervalent Si complexes have very recently been shown to form in the presence of aliphatic polyols and polyol acids, such as mannitol and saccharic acid, respectively. Such simple aliphatic hydrocarbons may play a crucial role in the uptake, transport, and deposition of Si in nature. The objective of this paper is to provide an overview of the speciation, equilibria, and chemical exchange kinetics of Si in aqueous environments, along with an examination of applicable methods of chemical analysis.

J. Götz

Papers

Determination of silicate anions by gas chromatographic separation and mass spectrometric identification of their trimethylsilyl derivatives

Chromatographic and mineralogical study of lunar fines and glass