The eluent was H2SO45 mM at 0.5 mL min−1 and the column temperature was 60◦C, maintained with a column thermostat. Citric acid concentration was measured by HPLC using aYMC ODS-Aq (250 × 4.6 mm)reverse phase column coupled to an UV detector at 214 nm. The mobile phase was KH2PO420 mM, pH 2.8 at room temperature and a flow rate of 0.7 mL min−1