Enantiomeric determination of proline in liquid food by high-performance liquid chromatography/mass spectrometry

Abstract

For the chiral separation and quantification of L-proline used as a food additive, a selective pretreatment method that uses o-pthalaldehyde (OPA) and 9-fluorenylmethyl chloroformate (FMOC-Cl) was examined, and HPLC/MS with high sensitivity and high selectivity was developed. Primary amino acids, which exist in liquid foods as impurities, were derivatized with OPA, followed by separation from proline with a solid-phase extraction cartridge. The secondary amino acids were converted into FMOC derivatives. Sample cleanup was achieved with this two-step derivatization method, and a selective pretreatment of secondary amino acids became possible. An excellent means to separate the optical isomer of proline was achieved using a chiral column made of a β-cyclodextrin phase in the polar organic phase mode. The average recovery rates of proline from soft drink, infant formula, and vinegar were as high as 80% to 104%. Using this method, proline in liquid food can be separated optically and determined. This method is expected to be of use in determining of the safety of proline used as a food additive. © 2007 The Japan Society for Analytical Chemistry.