Determination of α‐hydroxy acids and their enantiomers in fruit juices by ligand exchange CE with a dual central metal ion system

Abstract

The content of α-hydroxy acids and their enantiomers can be used to distinguish authentic and adulterated fruit juices. Here, we investigated the use of ligand exchange CE with two kinds of central metal ion in a BGE for the simultaneous determination of enantiomers of dl-malic, dl-tartaric and dl-isocitric acids, and citric acid. Ligand exchange CE with 100 mM d-quinic acid as a chiral selector ligand and 10 mM Cu(II) ion as a central metal ion could enantioseparate dl-tartaric acid but not dl-malic acid or dl-isocitric acid. Addition of 1.8 mM Sc(III) ion to the BGE with 10 mM Cu(II) ion to create a dual central metal ion system permitted the simultaneous determination of these α-hydroxy acid enantiomers and citric acid. The proposed ligand exchange CE was thus well suited for detecting adulteration of fruit juices.

Recent advances in the application of capillary electromigration methods for food analysis and Foodomics

“…The use of chiral metal complexes for enantioseparation following the chiral ligand exchange principle provides high selectivity of chiral molecules, and following this idea, d ‐isocitric, l ‐isocitric acid, and citric acids were separated using a ligand exchange CE method with Ni(II)‐ d ‐quinic acid system. Following a similar approach, but with different ligand exchange (namely, Sc(III)/Cu(II)‐ d ‐quinic acid system), enantiomers of d / l ‐malic, d / l ‐tartaric, and d / l ‐isocitric acids, as well as and citric acid, were analyzed . The content of these α‐hydroxy acids enantiomers was also used to distinguish authentic and adulterated fruit juices.…”

Quality control of fruit juices by using organic acids determined by capillary zone electrophoresis with poly(vinyl alcohol)-coated bubble cell capillaries

“…As observed in Table 1, LODs and LOQs ranged from 0.1 to 2.5 lg mL À1 and from 0.3 to 8.3 lg mL À1 , respectively. These values were lower than others previously published in literature for CZE methods (Kodama et al, 2013;Saavedra et al, 2000), although were higher than those reported using a Waters Capillary Ion analysis system at unusual short wavelength UV detection (185 nm) (Mato et al, 2006). Peak identification was performed by comparing migration times with those of the standards, and when necessary also by spiking the samples with the standards.…”

Some thoughts about enantioseparations in capillary electrophoresis

“…Another important group of chiral compounds related to food and beverage production are organic acids . These constituents (mainly present in the nature as single enantiomers) are responsible for a unique bouquet of wine, sake, cognac, juices, etc.…”