CHARACTERIZATION OF FLUORINATED ETHYLCHLOROFORMATE DERIVATIVES OF PROTEIN AMINO-ACIDS USING POSITIVE AND NEGATIVE CHEMICAL-IONIZATION GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A solution of ethyl chloroformate + trifluoroethanol (or ethanol) + py ridine reacts rapidly with carboxylic and amino groups of amino acids to form n-ethoxycarbonyl amino acid trifluoroethyl (or ethyl) esters, which produce strong peaks representative of molecular ions in both po sitive and negative chemical ionization gas chromatography/mass spectr ometry. Sensitivity of detection of the trifluoroethyl ester derivativ es versus ethyl ester derivatives in the positive and negative chemica l ionization modes is also discussed.