Determination of clemastine hydrogen fumarate, desloratadine, losartan potassium and moxepril HCl through binary complex formation with eosin

A simple and sensitive spectrophotometric method has been established for the determination of clemastine hydrogen fumarate (I), desloratadine (II), losartan potassium(III) and moxepril HCl(IV) based on binary complex formation with eosin. The method does not involve solvent extraction through the use of a non-ionic surfactant (methylcellulose). The color of the produced complex was measured at 552, 549 nm for (I), (II) while was measured at 540 nm for (III) and (IV). Appropriate conditions were established for the color reaction between eosin and the studied drugs to obtain maximum sensitivity. Under the proposed conditions, the method is applicable over concentration range of 1.25-11.25, 0.31-2.81, 2.5-20 and 1.25-15 μg/ml for (I), (II), (III) and (IV), respectively. The molar absorptivity (ε), sandell sensitivity, detection (LOD) and quantitation limits (LOQ) are calculated. Unlike other reported ion-pair techniques, the suggested methods have the advantage of being applicable for the determination of the four drugs in their pharmaceutical dosage forms without prior extraction with excellent recoveries.