Exploration of disaccharide as reference towards chiral recognition by the kinetic method

Abstract

Rationale: A potential use of disaccharides was found as reference compounds in the kinetic method for chiral recognition and enantiomeric quantification.

Methods: The experimental procedure consists of three steps: (1) mixing a metal salt, an analyte and a disaccharide at a molar ratio of 1:2:2 with an analyte concentration of 20 μM; (2) introducing the mixture into an electrospray ionization (ESI) mass spectrometry source; (3) isolating the ion [M^II (ref*)₂ (A) - H]⁺ and subjecting it to dissociation. Then through the relative ratio of two product ions combined with the kinetic method, chiral recognition and enantiomeric quantification can be achieved.

Results: The method was verified with good chiral recognition for ten chiral amino acids and three chiral drugs. Among the ten amino acids, Tyr was observed to show best chiral selectivity (R_chiral = 1.62) and good linearity with the correlation coefficient R² = 0.9991 for the quantitation of the enantiomeric excess (ee) of D-Tyr. Among the tested chiral drugs, naproxen showed best chiral selectivity with R_chiral = 1.56 and good linearity with the correlation coefficient R² = 0.9997 for the quantitation of the ee of R-naproxen.

Conclusions: This established approach proves that a disaccharide can serve as a reference compound for chiral recognition using the kinetic method.