Abstract
A simple, rapid, accurate, precise and sensitive spectrophotometric method for the determination of four analgesic drugs namely, tramadol (TRAM), morphine (MORF), nalbuphine (NALB) and naltrexone (NALT) in bulk sample and in dosage forms is described. The method is based on oxidation of the studied drugs by potassium permanganate in acidic medium and determination of the unreacted oxidant by measuring the decrease in the absorbance of indigo carmine (IC) dye at 610 nm. Under the optimum conditions, Beer's law limit, molar absorptivity and Sandell's sensitivity were calculated. The limits of detection and quantification were also reported. Statistical evaluation of the method was examined by determining an intra-day and inter-day precisions. The method was successfully applied to the assay of drugs in their pharmaceutical formulations. No interference was observed from common additives and the validity of the method was tested.