Application of Super Modified Simplex Optimization to the Flow Injection Spectrophotometric Determination of Promethazine Hydrochloride in Drug Formulations

An accurate reproducible flow injection spectrophotometric method for the assay of promethazine was developed using cerium(IV) as an oxidant. The super modified simplex program was utilized for the optimization of dependant parameters. In the method, a 110 μl drug sample was injected into a flowing stream of 6.19X10-4 M cerium(IV) dissolved in 0.512 M H2SO4. The reaction takes place in a reaction coil 62 cm long. Finally, the colored oxidized form of the drug was monitored at 515 nm. Promethazine in the range 60 - 200 ppm with a 200-sample/ h throughput was determined, 0.80% relative standard deviation being attained. The method was successfully applied to the determination of promethazine in proprietary drugs, its accuracy was statistically compared with the British Pharmacopoeia (BP) official method.