Supercritical fluid chromatographic method using phenyl packed column for determination of phenobarbitone and phenytoin sodium in dosage form Original Research Article

The separation and estimation of phenobarbitone and phenytoin sodium in pharmaceutical dosage form, using chromatography with methanol-modified supercritical fluid CO2 has been investigated with carbamazepine as the internal standard. The analytes were resolved using a Shendon-Phenyl 5 μm (250×4.6 mm) column, using 11.8% methanol in CO2 (1.5 ml min−1) as mobile phase and detection at 230 nm. The phenyl column showed the most favourable chromatographic parameters for analysis. The densities and polarities of the mobile phase were optimised for the effects of pressure, temperature and modifier concentration on the retention time. The study includes a successful attempt at quantification of the drugs. Chromatographic figures of merit, calibration data, and recovery of the drugs from spiked concentrations were determined to assess the viability of the method. Limits of detection (3×standard deviation) of the assay were 0.40 μg ml−1 for phenobarbitone and 0.20 μg ml−1 for phenytoin sodium. The method has been successfully used to analyse commercial solid dosage form of locally available tablets labelled to contain 30/50 mg of phenytoin sodium and 50 mg of phenobarbitone with good recoveries. The internal standard method using carbamazepine has been employed to estimate the drug content of the tablets. There was no interference from excipients.