Rapid microanalysis of anticonvulsants by high-performance thin-layer chromatography

A rapid microanalytical method is described for phenobarbital, phenytoin, primidone and carbamazepine utilizing high-performance thin-layer chromatography (HPTLC). This procedure incorporates a single extraction of a 50-microliter plasma sample. One tenth of the extract is concentrated and applied to the HPTLC plate by a Contact Spotter, chromatographically separated and quantitated by in situ ultraviolet reflectance densitometry. The coefficient of variation is less than 4% (n = 8), the extraction efficiency is approximately 95% and the minimum detectable amount of pure drug standards applied to and developed on the HPTLC plate is 5 ng or less for all four anticonvulsants.