Characterization of fluorinated ethylchloroformate derivatives of protein amino acids using positive and negative chemical ionization gas chromatography/mass spectrometry

Abstract

A solution of ethyl chloroformate + trifluoroethanol (or ethanol) + pyridine 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 positive and negative chemical ionization gas chromatography/mass spectrometry. Sensitivity of detection of the trifluoroethyl ester derivatives versus ethyl ester derivatives in the positive and negative chemical ionization modes is also discussed.