A simple, rapid and sensitive spectrophotometric method was developed for determination of bisoprolol hemifumarate, buspirone HCl and doxazosin mesylate in pure form and in pharmaceutical formulations. The method was based on aggregation of synthesized gold nanoparticles (Au NPs). Gold nanoparticles showed an absorption band at 520 nm. Upon interaction with the cited drugs, the band at 520 nm disappeared with formation of a new red shifted band at 616, 656 and 670 nm for doxazosin mesylate, bisoprolol hemifumarate and buspirone HCl, respectively. Different experimental factors were optimized for higher sensitivity. The calibration curves were linear with concentrations of 3-14, 0.1-1.2 and 0.2-1.0 μg/mL for bisoprolol hemifumarate, buspirone HCl and doxazosin mesylate, respectively. The method was applied successfully to determine the studied drugs in minor concentrations in pure form and in their pharmaceutical dosage forms.

A simple and sensitive method was developed for spectrophotometric determination of etilefrine hydrochloride, salbutamol sulphate and tiemonium methyl sulphate in pure form and in their pharmaceutical formulations. The method was based on reduction of gold solution to gold nanoparticles by the studied drugs in presence of sodium dodecyl sulphate as stabilising agent. Gold nanoparticles (Au NPs) showed a new absorption band at 530 nm that was used for quantitative determination of the cited drugs. Different variables were examined and optimised in the experiment as gold solution concentration, type of buffer, suitable pH, stabilising agent, order of addition, time and temperature of the reaction. Under optimum conditions, the calibration curves were linear with concentration ranges of 3.0-20.0, 5.0-18.0 and 2.0-26.0 μg/mL for etilefrine Hydrochloride, salbutamol sulphate and tiemonium methyl sulphate respectively. The method was applied successfully to determine the studied drugs in pure form and in their pharmaceutical dosage forms, exhibiting good reproducibility and accuracy.