Determination of alpha hydroxy acids in fruits by capillary electrophoresis.

Alpha hydroxy acids, malic acid, citric acid, tartaric acid, glycolic acid and lactic acid, were analyzed simultaneously using capillary electrophoresis with direct UV detection at 200 nm. The separation was carried out with uncoated fused-silica (50 cm x 50 microns i.d.), pressure injection at 15 psi s and operated at -15 kV potential. The separation buffers were prepared with 180 mM Na2HPO4, 1 mM cetyltrimethylammonium bromide and 15% (v/v) methanol and adjusted to pH 7.2 by phosphoric acid. Validation was performed for citric acid and malic acid. The obtained parameters were adequate and the limits of detection were 2.5 and 5 micrograms ml-1 for citric acid and malic acid, respectively. AHAs from natural fruit juices (orange and grape) were determined and measured with this method.