Chiral x Achiral Multidimensional Liquid Chromatography. Application to the enantioseparation of dintitrophenyl amino acids in honey samples and their fingerprint classification

Abstract

Most HPLC enantiomer separations are performed with columns packed with a chiral stationary phase (CSP) operated with an achiral mobile phase. The intrinsically limited chemical selectivity of most CSPs to the simultaneous resolution of several pairs of enantiomers means that complex mixtures of diverse pairs of enantiomers cannot be analyzed in one run due to peak overlapping. Moreover, some drawbacks remain when the analyte is present in very complex samples containing other achiral compounds which can co-elute with the enantiomer peaks. Multidimensional chromatography becomes an option to increase peak capacity. The aim of this work was to study an on-line full comprehensive 2D-LC mode based on the combination of a chiral column in the first dimension and an achiral column in the second dimension. The 2D-LC system was built with an active flow splitter pump in order to easily adjust the volume of sample transferred to the second dimension and to choose independently the flow rate in the first dimension, typically a larger one than the Flow necessary to fill the sample loops. The present LCxLC method was optimized for the separation of amino acids present in honey samples, taking sampling frequency, etc.). Amino acids have been previously preconcentrated on a cation-exchange column followed by derivatization. Several amino acids present in different honey samples have been identified and data have been analyzed by principal component analysis.