M. Donike
Jan 14, 1975
Citations
0
Influential Citations
64
Citations
Journal
Journal of Chromatography A
Abstract
Abstract N-trifluoroacetyl-O-trimethylsilyl-phenolalkylamines. Preparation and mass specific gas chromatographic estimation N-TFA-O-TMS derivatives of phenolalkylamines are relatively stable compounds which are well suited for identification by combined gas chromatography and mass spectrometry. They are easily prepared by trimethylsilylation with N-methyl-N-trimethylsilyltrifluoroacetamide followed by selective N-acylation with N-methyl-bis(trifluoroacetamide). This technique of derivatisation can be applied to salts of phenolalkylamines without prior liberation of the bases. The thermodynamic and the kinetic aspects of the trimethylsilylation and N-trifluoroacetylation reactions are discussed. A definition is given of the “relative trimethylsilylation potential” of N-TMS-acetamides, which is based on gas chromatographic data. It is not necessary to evaporate the reaction medium, because the excess reagents and the remaining N-methyl-trifluoroacetamide, which originate from the trimethylsilylation as well as from the acylation step are extremely volatile and do not affect the gas chromatographic analysis. N-TFA-O-TMS-phenolalkylamines are stable against oxidising agents and at elevated temperatures. They do not show any adsorption effects in the molecular separator and in the gas chromatographic system. Solutions of catecholamines, for example, are stable for months, provided humidity is excluded. After electron impact the charge localisation predominates at the benzylic fragment, which gives information on the hydroxylic substitution pattern of the aromatic ring and the β-C-atom. The detection limits have been found to lie in the fernto mol region, when this structure-specific benzylic ion is registered in the single-ion fashion.