Spectrophotometric determination of drug compounds in pure forms and in the pharmaceutical preparations

A "Simple, sensitive and rapid" spectrophotometric method for determination of drug compounds (I) "Dextromethorphan HBr (Dex) and (II) Trimethoprim (Tri)" in both pure forms and pharmaceutical formulations. These methods were based on the oxidation of the studied drugs in presence of acidic medium by a known excess of "N – Bromosuccinimide" as an oxidizing agent and subsequent determination of unreacted oxidant by reacting it with: (I) Phenosafranine (PS) dye [3,7-Diamino-5-phenylphenazin-5-ium chloride] to produce red product at λ_max. 532 nm. The linearity range was found to be (6-56)μg/mL and molar absorptivity 4.686×10³ L/mol.cm, correlation coefficient 0.9983 and the limit of detection 0.763 μg/ml, with slope, intercept and %RSD were 0.0133, 0.3069 and 0.367 respectively. (II) Crystal Violet (CV) dye [4 [bis [4 (dimethylamino) phenyl] methylidene] cyclohexa-2,5-dien-1-ylidene]-dimethylazanium;chloride to produce blue product at λ_max. 590 nm. The linearity range was found to be (5-65)μg/ml and molar absorptivity 8.042×10³ L/mol.cm, correlation coefficient 0.9980 and the limit of detection 1.07 μg/ml, with slope, intercept and %RSD were 0.0277, 0.2558 and 0.273 respectively. These methods were successfully applied for the determination of (Dex) and (Tri) in tablets formulations. (paper)