N-Ethoxycarbonylation combined with ( S)-1-phenylethylamidation for enantioseparation of amino acids by achiral gas chromatography and gas chromatography–mass spectrometry

Abstract

N-Ethoxycarbonylation was combined with ( S)-1-phenylethylamidation for enantioseparation of amino acids by gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS) on achiral capillary columns. The method provided complete enantioseparations of 12 amino acids as diastereomeric N-ethoxycarbonyl/( S)-1-phenylethylamides with exceptional resolutions for proline ( R s ≥ 9.9) and pipecolic acid ( R s ≥ 10.2). GC–MS analysis in selected ion monitoring mode employing standard addition method, facilitated quantitation of d-pipecolic acid in kidney bean (0.95 μg/10 mg) and adzuki bean (0.14 μg/10 mg). The peak area ratios indicated that they had the identical chiral composition at 2.5% for d-pipecolic acid and 97.5% for l-pipecolic acid.