Determination of ursodeoxycholic acid in pharmaceutical preparations by capillary electrophoresis with indirect UV detection.

A simple and rapid capillary electrophoretic method, with indirect UV detection, for the quantification of ursodeoxycholic acid (UDCA) in pharmaceutical preparations was developed in this study. Sodium p-hydroxy benzoate was used as background electrolyte (BGE) (5 mM, pH 8.0) and visualization agent. Separation was carried out on a fused-silica capillary (50 microm x 72 cm) at a potential of 25 kV under ambient temperature and detected at 250 nm. Glycocholic acid was used as internal standard for quantification. Both run-to-run repeatability and day-to-day reproducibility of migration time were below 0.1% relative standard deviation (R.S.D.). Repeatability and reproducibility of relative peak height were 3.3 and 3.8% R.S.D., respectively. Accuracy was tested by spiking two pharmaceutical tablets with standards and the recoveries were 101.9+/-9.87 and 99.6+/-9.60% (n=3), respectively. Linearity of relative peak height was tested in the range 20-100 microg/ml. Limit of detection (LOD) was 3 microg/ml. The method could be used to assay UDCA raw materials and formulation products.

Analysis of lignans using micellar electrokinetic chromatography.

Micellar electrokinetic chromatography (MEKC) was used to separate twelve lignan compounds originating from Phyllanthus plants. To increase the reliability of peak identification, two micellar systems, the sodium dodecyl sulfate (SDS) and sodium deoxycholate (SDC) systems, were investigated. Because of the high lipophilicity of the lignan analytes, tetrahydrofuran was added to the SDS micellar system to increase its separating ability. In contrast to SDS system, no organic solvent was needed with SDC micelles. Both micellar systems gave a satisfactory separation within a reasonable analysis time. On considering accuracy for quantitation, the SDS method was validated and then used to determine the content of the lignans in two Phyllanthus plants. The selectivity (elution order of the lignans) was significantly different between the SDS and SDC micellar systems. Retention in SDC-MEKC seemed to be dominated by the hydrophobicity of the lignan solutes, while in SDS-MEKC, retention was greatly influenced by hydrogen bonding interactions.