Direct chiral resolution of lactic acid in food products by capillary electrophoresis

Chiral resolution of native dl-lactic acid was performed by capillary electrophoresis using 2-hydroxypropyl-β-cyclodextrin as a chiral selector. Various factors affecting chiral resolution, migration time, and peak area of lactic acid were studied. The running conditions for optimum separation of lactic acid were found to be 90 mM phosphate buffer (pH 6.0) containing 240 mM 2-hydroxypropyl-β-cyclodextrin with an effective voltage of −30 kV at 16°C, using direct detection at 200 nm. In order to enhance the sensitivity, sample injection was done under a pressure of 50 mbar for 200 s. On-line sample concentration was accomplished by sample stacking. With this system, d- and l-lactic acids in food products were analyzed successfully.