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Determination of the enantiomers of α-hydroxy- and α-amino acids in capillary electrophoresis with contactless conductivity detection

Pormsila, Worapan, Gong, Xiao Yang, Hauser, Peter C.
Electrophoresis 2010 v.31 no.12 pp. 2044-2048
absorbance, anions, aspartic acid, capillary electrophoresis, correlation, enantiomers, glutamic acid, lactic acid, milk, vancomycin, yogurt
The enantiomers of the anions of five α-hydroxy acids, namely lactic acid, α-hydroxybutyric acid, 2-hydroxycaproic acid, 2-hydroxyoctanoic acid and 2-hydroxydecanoic acid, as well as the two α-amino acids aspartic acid and glutamic acid, were baseline separated and detected by CE with contactless conductivity detection. Vancomycin was employed as chiral selector and could be used with conductivity detection without having to resort to a partial filling protocol as needed when this reagent is used with UV absorbance measurements. The procedure was successfully applied to the determination of the lactic acid enantiomers in samples of milk and yogurt. Linearity was achieved in the concentration range of 10-500 μmol/L with good correlation coefficients (0.9993 and 0.9990 for L- and D-lactic acid, respectively). The LODs (3 S/N) for L- and D-lactic acid were determined as 2.8 and 2.4 μmol/L, respectively.