Spectrophotometric determination of promethazine HCl in pure and dosage forms

Background: The research is involved development a new spectrophotometric method based on the oxidative coupling reactions for determination of important phenothiazine drug which is promethazine HCl in pure solutions and local pharmaceutical preparations. Materials and methods: The Standard promethazine HCl was treated with organic reagent of P-Chloroaniline as a coupling reagent in the presence of oxidizing agent Ammonium Cerric (IV) Sulphate, the reaction leads to the formation a blue –greenish color product that has a maximum absorption at 603nm. Results: The variables of reaction conditions including optimum volumes of both reagent and oxidizing agent, acidity of the reaction medium, order of addition and stability time were studied. The obtained results of the purposed method shows that a Beer law is obeyed in the range of 7-40ppm with a correlation coefficient (r2) of 0.9981. While the molar absorptivity (ξ) of 1.861x103 L.mol-1.cm-1, sandal sensitivity(s) of 0.172μg.cm-2, limit of detection (LOD) of 4.02ppm and limit of quantification (LOQ) of 13.39ppm were obtained. The developed method was compared with the standard method adopted by USP using F and t-tests and the results shows no significant deferent between both methods. Conclusion: The analytical method was also applied successfully for pharmaceutical preparations containing promethazine HCl.