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A simple and inexpensive high performance capillary electrophoresis (HPCE) was applied to separate five benzoic acid compounds simultaneously. The investigation was carried out by micellar electrokinetic capillary chromatography (MECC). To avoid a time-consuming and tedious procedure, orthogonal experimental design OA 9 (3 4 ) for separation experiments was applied to find the optimal conditions in terms of the resolution and analytical time. The best conditions for separation were obtained using a 20 mM borax and 30 mM sodium dodecyl sulfate (SDS) buffer (pH 9.8) containing 2 mM b-CD and 4% methanol (v/v). Online UV detection was performed at 250 nm. A voltage of 16 kV was applied and the temperature was controlled at 25°C. Injection was performed for 5 s. The method was validated for the quantification of benzoic acid, salicylic acid and ortho-aminobenzoic acid in Radix Isatidis, a traditional plant medicine with removal of endotoxin. The separation and determination were satisfactory and quick.

Abstract.A simple, sensitive and inexpensive method for determination of diacerein by flow-injection chemiluminescence was proposed, based on the quenching effect of diacerein on the luminol-protein (bovine serum albumin, BSA) reaction. It was found that the decrement of CL intensity was linearly proportional to the logarithm of diacerein concentration ranging from 5.0 to 7.0×103 pg·mL-1 (r = 0.9968), with the limit of detection (LOD) of 1.0 pg·mL-1 (3σ). The proposed procedure was successfully applied to the determination of diacerein in pharmaceutical formulation, human saliva, and serum samples without interference from its potential impurities, with the recoveries ranging from 96.4% to 104.0% and the relative standard deviations (RSDs) less than 4.0% (n=6).