Use of t-butyldimethylsilylation in the gas chromatographic/mass spectrometric analysis of physiologic compounds found in plasma using electron-impact ionization

The use of N-methyl-N-(t-butyldimethylsilyl)trifluoroacetamide to prepare the t-butyldimethylsilyl derivatives of a number of organic compounds (selected amino acids, α-keto acids, ketone bodies, free fatty acids, urea, glycerol, lactate, and pyruvate) is reported. These derivatives are particularly useful for gas chromatographic/mass spectrometric analysis involving the use of stable isotopes and selected ion monitoring, since a peak of sufficient abundance at 57 mass/charge units below the molecular ion was always present, and was the result of the loss of one t-butyl group. In each case, this fragment contained the entire skeleton of the original compound, which permitted easy analysis using electron-impact ionization of these compounds alone or when labeled with stable isotopes in any nonexchangeable position.