Determination of Captropril using adsorptive cathodic differential pulse stripping voltammetry with the HMDE

Highly sensitive voltammetric determination of captopril on renewable amalgam film electrode

New highly sensitive voltammetric method for captopril (CPT) determination was developed. The main novelty of the work was the application of a renewable amalgam film electrode (Hg(Ag)FE) for this purpose. During the research instrumental parameters of the developed method were optimized and were as follows: t_w = t_s = 5 ms, E_s = 5 mV, ΔE = 100 mV. Preconcentration potential and time were equal to 100 mV and 20 s, respectively. All measurements were conducted in electrolyte consisted of 0.1 M HClO₄. Limit of detection was calculated and was equal to 1.9 nM (0.39 ng mL^-1) for 20 s preconcentration time and Hg(Ag)FE surface area approximately 11.2 mm². Linearity was achieved in the concentration range 0.05-1 μM. Repeatability of the method expressed as variation coefficient was estimated at 3.5% (0.15 μM CPT, n = 10). Applicability of the method was confirmed by analysis of tablets containing CPT and urine. Recoveries were in the range from 95 to 109% suggesting that the method might be assumed as accurate. Obtained results were also in good agreement with the producer declaration.

A study of the determination of the hypertensive drug captopril by square wave cathodic adsorptive stripping voltammetry

In this work, the determination of captopril (CPL) was studied by square wave cathodic adsorptive stripping voltammetry (SWCAdSV) on a hanging mercury drop electrode (HMDE). CPL was adsorptively preconcentrated on the mercury surface as a sparingly soluble mercury salt under stirring of the solution and then the accumulated species was reduced by a cathodic square wave voltammetric scan. The reduction current was related to the CPL concentration in the sample. The chemical and instrumental parameters affecting the response were investigated and optimized for the CPL determination. The calibration curve was linear from 0.5 to 180 microg l(-1) of CPL (depending on the preconcentration time), the limit of detection at a S/N ratio of 3 was 0.5 microg l(-1) with 300 s of preconcentration and the relative standard deviation was 3.2% at the 20 microg l(-1) level (with 120 s of preconcentration, n=8). The method was applied to the determination of CPL in two pharmaceutical formulations with recoveries of 97.9 and 98.8%. Finally, the potential for applying the proposed method to the determination of CPL in biological media is briefly discussed.

Fluorimetric determination of some thiol compounds in their dosage forms

A simple fluorimetric procedure was adopted for determination of three pharmaceutical compounds containing thiol groups namely, captopril, D-penicillamine and N-acetylcysteine. In this method, the drugs are treated with 1,2-naphthoquinone-4-sulfonic acid. The latter is reduced to 1,2-dihydroxynaphthalene-4-sulfonic acid which has a maximum fluorescence intensity at 480/318 nm (lambdaEm/Ex). The method is sensitive to 0.5-4.5 pg ml(- 1) with minimum detectability 0.05 microg ml(-1) (S/N = 2), and has been applied to determine these three thiols in their dosage forms. The results obtained are compared favourably with those obtained by their pharmacopeial methods.

Spectrophotometric investigation on complex formation of captopril with palladium(II) and its analytical application

The formation of the complex between captopril and palladium(II) chloride in Britton-Robinson buffer solution was studied. It has been established that captopril reacts with palladium(II) chloride in the pH range 2.14-9.10 to form a yellow water--soluble 2:1 complex with maximum absorbance at 380 nm. By applying different spectrophotometric methods, the conditional stability constant of the complex at the optimum pH of 4.03 and ionic strength mu = 0.5 M was found to be 108.25). The molar absorptivity was 1.875 x 10(3) l mol-1 cm-1. Beer's law was obeyed in concentrations up to 5 x 10(-4) M captopril. The detection limit was 2.17 micrograms ml-1 and the relative standard deviation varied from 1.24 to 1.68%. The proposed method was found to be suitable for the accurate and reproducible analysis of captopril in water and in tablets.

Determination of captopril in pharmaceutical samples by flow injection analysis

A flow injection spectrophotometric method for the determination of captopril involving measurement of the absorbance of the captopril complex with palladium(II) in a 0.12 M HCl medium at 400 nm is presented. The calibration graph was linear over the range 2 x 10(-5)-6 x 10(-4) M. The sampling frequency was 90 h-1 with sample injections of 70 microliters. The proposed method was applied to the determination of captopril in pharmaceutical samples.