Application of certain ion – pairing reagents for extractive spectrophotometric determination of flunarizine hydrochloride, ramipril and terbinafine hydrochloride

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Three simple, rapid and extractive spectrophotometric methods have been developed for the determination of flunarizine hydrochloride (F.HCl), ramipril (RAM) and terbinafine hydrochloride (T.HCl). The proposed methods depend on the formation of colored ion-pair complexes between the basic nitrogen of the drug and the inorganic complex; molybdenum (V) thiocyanate, Mo(V) (SCN) or the acid dyes; orange G (OR.G) and alizarin red S (ARS). The formed complexes were extracted with the suitable organic solvent and measured at 469 -471 nm for Mo(V) (SCN) method; 498-500 nm using (OR.G) method and at 425 -426 nm in case of (ARS). The analytical parameters and their effects on the reported systems were investigated. The methods permit the determination of the studied drugs over a concentration range of 5-75 μg ml-1, 10-80 μg ml-1 and 5- 55 μg ml-1 using Mo(V), (OR.G) and (ARS) respectively. The composition of the ion-pairs was found by Job’s method. The proposed methods were applied for the analysis of drug substances in their dosage forms and the results obtained were in good agreement with those obtained by the official and reference methods.

Flunarizine HCl; Ramipril; Terbinafine HCl; Molybdenum (V) thiocyanate; Orange G; Alizarin red S