Determination of adulteration in apple juice by HPLC with novel optical rotation detector.

A simple HPLC method for the determination of adulteration in apple juice was developed. The method is based on the detection of d-malate, derived from racemic malic acid, which is added as an acidulant. A variable-wavelength optical rotation detector was used to determine the enantiomeric excess (ee). Using anion-exchange chromatography with a phosphate buffer eluent and UV (210 nm) detection, the limit of detection for l-malate was 2 μg. With an injection of 13.4 μg of malate, the standard deviation of the ee calibration curve was 2.5%. Several apple juice samples were analyzed according to the proposed procedure, and the results agreed with those obtained using enzymatic kits for food analysis.