Determination of Benzoic Acid, Salicylic Acid and o-Aminobenzoic Acid in Radix Isatidis by Micellar Electrokinetic Capillary Chromatography

Micellar electrokinetic capillary chromatography (MECC) was applied to the separation and determination of aromatic acids, including benzoic acid, salicylic acid and o-aminobenzoic acid, in Radix Isatidis. A mixed buffer solution of pH 9.8 containing 20 mmol·L-1 borate, 30 mmol·L-1 SDS, 2 mmol·L-1 β-CD and 4% (by vol.) methanol was used as the electrophoretic medium. p-Hydroxybenzoic acid was chosen as internal standard. Separation voltage applied was 16 kV and wavelength of detection was taken at 250 nm. Under the optimum conditions, linearity ranges of benzoic acid, salicylic acid and o-aminobenzoic acid found were between 40-240, 64-320 and 40-400 mg·L-1, with detection limits (3S/N) of 0.64, 1.08, 1.36 mg·L-1 respectively. The proposed method was used in the analysis of sample of Radix Isatidis, giving values of recovery in the range of 93.3%-104.2%.