QUANTITATIVE-ANALYSIS OF FLUORINATED ETHYLCHLOROFORMATE DERIVATIVES OF NONPROTEIN AMINO-ACIDS USING POSITIVE AND NEGATIVE CHEMICAL-IONIZATION GAS CHROMATOGRAPHY-MASS SPECTROMETRY

The GC-MS characterization of the ethylchloroformate derivatives of am ino acids in an aqueous medium has been applied to non-protein amino a cids. Derivatization of non-protein amino acids using ethylchloroforma te, trifluoroethanol, and pyridine produced strong [M + 1](+) and [M - 1](-) ions in positive and negative chemical ionization (CI) modes, r espectively. Twenty-one out of the twenty-three non-protein amino acid s studied produced detectable ion chromatograms in both ionization mod es when methane was used as the CI reagent gas. Mass spectra of these non-protein amino acid derivatives showed characteristic [M - 19](+), [M + 1](+), [M + 29](+), and [M + 41](+) peaks in the positive chemica l ionization mode, and [M - 1](-), and [M + 35](-) peaks in the negati ve chemical ionization mode. The detection limits and the linear dynam ic range of trifluorethanol ethylchloroformate derivatives of non-prot ein amino acids were studied using positive chemical ionization. The d etection limits are mostly in the femtomole range.