Determination of organic acids in apple juice by capillary liquid chromatography

The organic acids quinic, malic, shikimic and citric were separated on a packed reverse phase fused-silica capillary column using 0.01 M K2HPO4/H3PO4 at pH 2.7 as eluent at a flow rate of 2 mu L/min, and determined with UV detection. Conventional liquid chromatographic equipment was adapted for such purposes. The organic acids were able to be separated with detection limits of 2.4, 2.1, 0.04 acid 2.9 ng, respectively. Application of the proposed method to the quantification of organic acids in apple juice is reported.