Development of a simultaneous two-dimensional micro-HPLC analysis system for the chiral amino acid metabolomics study in mammals

D-Amino acids, enantiomers of L-amino acids, are increasingly recognized as being novel physiologically active substances and biomarkers in higher animals, including human beings. Although L-amino acids are abundantly present in the tissues and physiological fluids, the amounts of their enantiomers, D-forms, are extremely small in most cases. Therefore, for the precise analysis of small amounts of D-amino acids, a highly sensitive and selective analytical method is essential. In the present article, a two-dimensional micro-HPLC procedure combining a reversed-phase column and an enantioselective column is described for chiral amino acid metabolomics studies in mammals.