VALIDATED SPECTROPHOTOMETRIC METHOD TO DETERMINE VARDENAFIL AND SILDENAFIL IN PHARMACEUTICAL FORMS USING POTASSIUM IODIDE AND POTASSIUM IODATE

摘要

Objective : To develop and validate simple, sensitive, precise and free of organic solvents method for the determination of sildenafil (SIL) and vardenafil (VAR) in bulk and pharmaceutical formulation. Methods : The method is based on the reaction of studied drugs with a mixture of potassium iodide and potassium iodate in an aqueous medium at (25±2 °C) to form yellow coloured triiodide ions (I 3 - ) within 45 min. The reaction is followed spectrophotometrically by measuring the absorbance at 288, 351 nm and 285, 351 nm for sildenafil and vardenafil respectively. Results : The effects of analytical parameters on the reported systems were investigated. Beer's law of SIL was obeyed in the range of (0.4-12) μg ml -1 and (0.6-16) μg ml -1 . Molar absorptivity was found to be (67.659 ×10 3 ) lmol/cmand (37.955×10 3 ) lmol/cm at 288 nm, 351 nm respectively. Beer's law of VAR was obeyed in the range of (0.2-13) μg/mland (0.5-40) μg/ml. Moreover, molar absorptivity’s were found to be (68.719 ×10 3 ) l mol -1 cm -1 and (26.691×10 3 ) l mol -1 cm -1 at 285 nm, 351 nm respectively. Conclusion : The proposed method has been applied to determine the components in dosage forms with an average recovery of 98.15% to 103.45% and the results have been found in good agreement with those results obtained by the reference methods .