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) > or = 9.9) and pipecolic acid (R(s) > or = 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 microg/10 mg) and adzuki bean (0.14 microg/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.