Micellar liquid chromatographic determination of anti-convulsant drugs in pills and capsules

A simple chromatographic procedure is reported for the determination of sev eral anti-convulsant drugs in pharmaceuticals: carbamazepine, and the benzo diazepines bentazepam, halazepam, oxazepam, pinazepam, and tetrazepam. The procedure utilizes a C-18 column, a hybrid micellar mobile phase of 0.1 M S DS-3% butanol-0.1% triethylamine-0.01 M phosphate buffer (pH 3), and UV det ection (230 nm). The drugs eluted in less than 13 min, in accordance to the ir relative polarities, as indicated by their octanol-water partition coeff icients. The limits of detection (mu g/mL), and intra and inter-day repeatabilities (%), for 4 mu g/mL were: carbamazepine (0.03, 1.0, 4.1), bentazepam (0.05, 1.3, 1.6), halazepam (0.10, 2.3, 1.3), oxazepam (0.02, 0.9, 7.9), pinazepam (0.01, 0.3, 5.1), and tetrazepam(0.03, 1.1, 6.3). The results were compare d with those obtained in a conventional procedure using methanol-water 70:3 0 (v/v). The contents evaluated with the micellar mobile phase always agree d with the declared compositions, instead, with the aqueous-organic mobile phase, pinazepam gave poor recoveries and halazepam did not elute at approp riate times.