Capillary zone electrophoresis of organic acids in beverages

Capillary zone electrophoresis (CZE) with photodiode array detection (PDA) was applied to simultaneously determine eleven organic acids in wine, beer, and fruit and vegetable juices after derivatisation with 2-nitrophenylhydrazine (2-NPH) in the presence of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC·HCl). The parameters affecting CZE separation included type and concentration of buffer, pH, organic additive and applied voltage. Optimum conditions at 25 °C were: 30 mmol l−1 borate buffer, pH 10.0, containing 100 ml l−1 acetonitrile, at 20 kV, sample injection at 0.5 psi for 5 s, with direct detection at 230 nm. Separation of eleven organic acids was achieved within 12 min. Linear calibration curves with good fit were obtained in the range 10.0–100.0 mg l−1. Limits of detection ranged from 2.0 to 10.0 mg l−1. Intra-day precision with RSD⩽4.0% for migration time and ⩽5.0% for peak area, and inter-day precision with RSD⩽6.0% and ⩽9.0% for migration time and peak area, were obtained. Recovery for all beverage samples was 97±15%.