Use of Cycloalkylcarbonyl Derivatives for the Determination of Amino Acid Methyl Esters by Gas Chromatography–Mass Spectrometry

Cycloalkylcarbonyl (cycloalkyl = cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl) derivatives were proposed for the determination of amino acid methyl esters by gas chromatography–mass spectrometry. These compounds are readily formed with the quantitative yield on heating hydrochlorides of amino acid methyl esters with cycloalkylcarbonyl chlorides. Although these derivatives exhibit lower chromatographic mobility than acetyl or perfluoroacyl derivatives, they form symmetric peaks. Mechanisms of the fragmentation of the new class of compounds under electron ionization conditions were studied in detail using high-resolution mass spectra and analysis of metastable ions. It was demonstrated that cyclopentylcarbonyl and cyclohexylcarbonyl derivatives can decompose with the cleavage of carbocycles.