Analysis of 3-chlorotyrosine as a specific marker of protein oxidation: the use of N(O,S)-ethoxycarbonyltrifluoroethyl ester derivatives and gas chromatography/mass spectrometry.

N(O,S)-ethoxycarbonyltrifluoroethyl amino acid esters are formed by the reaction of amino acids with ethylchloroformate plus trifluoroethanol plus pyridine. The use of these derivatives for a rapid and sensitive determination of 3-chlorotyrosine, a highly specific marker of myeloperoxidase-catalyzed protein oxidation, by using standard gas chromatography/electron impact mass spectrometry, is discussed.