Spectrophotometric methods for determination of enalapril and timolol in bulk and in drug formulations

Abstract

Two simple and accurate spectrophotometric methods for determination of timolol and enalapril maleate are described. The first method is based on chelate formation with palladium(II) chloride in buffered medium. The second method is based on the formation of the colored complex between palladium(II), eosin, and the two cited drugs using methylcellulose as surfactant to increase the solubility and intensity of the formed complexes. Under optimum conditions the complexes showed maximum absorption at 369.4 nm and 362.8 nm for timolol and enalapril maleate, respectively, in the first method and 552.2 and 550.6 nm for the second method. Apparent molar absorptivities were 1.8 x 10(3) and 1.3 x 10(3) and Sandell's sensitivities were 5.9 x 10(-4) and 2.7 x 10(-4) for timolol and enalapril maleate in the first method; in the second method molar absorptivities were 2.8 x 10(4) and 1.1 x 10(4) while Sandell's constants were 9.1 x 10(-3) and 2.3 x 10(-3) for timolol and enalapril maleate. The solutions of the complexes obeyed Beer's law in the concentration ranges 20-200 micro g mL(-1) and 50-300 micro g mL(-1) for timolol and enalapril maleate, respectively. In the second method, because the reaction was more sensitive the ranges were reduced to 1.6-16 micro g mL(-1) for timolol 8-56 micro g mL(-1) for enalapril maleate. The proposed methods were applied to the determination of the two drugs in their pharmaceutical formulation.

Extractive Colorimetric Method for the Determination of Dothiepin Hydrochloride and Risperidone in Pure and in Dosage Forms

“…[21][22][23][24][25] In the present study, the formed ternary complexes consist of the cited drug I or II as the main ligand, thiocyanate as a second ligand, and the metal ions. Different metal ions were examined (copper, nickel, iron, zinc and cobalt).…”

Development and Validation of HPLC Method for Simultaneous Estimation of Brimonidine Tartrate and Timolol Maleate in Bulk and Pharmaceutical Dosage Form

“…BP estimated Timolol Maleate potentiometrically [13]. Literature review reveals several methods have been reported for the estimation of Timolol Maleate in biological fluids [14][15][16][17][18][19] and there are some methods reported by voltammetry [20], spectroscopy [21][22][23], HPTLC [24] HPLC [25][26][27][28], UPLC [29,30] and capillary electrophoresis [31]. Two methods were only reported for estimation of this combination, the first is HPTLC [32] and the other is HPLC method [33].…”

Direct Spectrophotometric Determination of Atenolol and Timolol Anti-Hypertensive Drugs

“…1b), is used as an antihypertensive and an antiglaucoma agent. Literature survey revealed that few methods have been reported for the determination of TIM in pharmaceutical preparations such as spectrophotometric methods [28][29][30]. Here, also, derivative ultraviolet [31,32], high-performance liquid chromatography [33,34], liquid chromatography [35], chemiluminescence [36] and electrophoresis [37].…”