Voltammetric determination of cilazapril in pharmaceutical formulations

Stripping voltammetric behaviour of toxic drug nitrofurantoin

A simple, sensitive and reproducible squarewave cathodic adsorptive stripping voltammetric method has been developed for the determination of nitrofurantoin in solubilized system. The objective of the present paper is to investigate the redox behaviour of nitrofurantoin by using different voltammetric techniques and to establish the methodology for its determination in the presence of surfactants. Voltammograms of the drug with cetrimide in phosphate buffers of pH 2-11 exhibited a single well-defined reduction peak which may be attributed to the reduction of -NO(2) group. The reduction process is irreversible over the entire pH range studied. The mechanism of reduction has been postulated on the basis of controlled potential electrolysis, coulometry and spectral analysis. The proposed SWCAdSV voltammetric method allows the determination of nitrofurantoin in linear concentration range 2 x 10(-5) to 1 x 10(-7) mol L(-1). The lower limit of detection (LOD) and lower limit of quantification (LOQ) are 0.06 and 0.27 ng/mL, respectively.

Adsorptive stripping voltammetric behavior and determination of anticholinergic agent oxybutynin chloride on a mercury electrode

Oxybutynin chloride is an antispasmodic, anticholinergic agent indicated for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and frequency. Its electrochemical behavior in phosphate buffers of pH range 2-10 at a hanging mercury drop electrode has been investigated using cyclic voltammetry, differential pulse cathodic adsorptive stripping voltammetry (DPCAdSV), and squarewave cathodic adsorptive stripping voltammetry (SWCAdSV). Voltammograms of the drug in phosphate buffer of pH 2-10 exhibited a single two-electron wave and it may be attributed to the reduction of the C[triple bond]C center. Based on the high adsorptive character of oxybutynin chloride onto the mercury electrode, a validated direct squarewave cathodic adsorptive stripping voltammetric and differential pulse cathodic adsorptive stripping voltammetric procedure has been developed for the determination of drug in bulk form and pharmaceutical formulation. The proposed SWCAdS and DPCAdS voltammetric methods allow quantitation over the range 1-18 and 1-17.6 microg mL(-1) with detection limits of 0.1 and 0.23 microg mL(-1), respectively. Precision and accuracy were also checked and were within the limits.

Square wave voltammetric determination of the angiotensin-converting enzyme inhibitors cilazapril, quinapril and ramipril in pharmaceutical formulations

The angiotensin-converting enzyme inhibitors cilazapril, quinapril and ramipril are reduced at a hanging mercury drop electrode in the pH range 3.5-13 using Britton-Robinson buffers as supporting electrolyte and KCl as ionic medium. Square wave voltammetry has proved to be the most suitable electroanalytical technique for the quantitative voltammetric determination of these antihypertensive drugs. Optimisation of the chemical and instrumental variables was carried out. Analyses were performed in 0.02 M borate buffer at pH 9.5 and 0.5 M KCl as ionic medium, using a pulse amplitude of 50 mV and a frequency of 150 Hz. A linear relationship between peak current and concentration was found in the interval 0.5-8 microg/ml for cilazapril and up to 6 microg/ml for quinapril and ramipril, allowing the direct determination of their pharmaceutical formulations alone or mixed with hydrochlorothiazide. Good accuracy and repeatativity were obtained.