Flow-Injection Spectrophotometric Determination of Captopril Exploiting Silver Chloranilate Solid-Phase Reactor

Smartphone application for captopril determination in dosage forms and synthetic urine employing digital imaging

A simple, accurate, and low-cost analytical procedure for captopril determination through digital imaging is presented. The method relies on the spot test reaction between captopril and palladium (II) chloride, which produces a yellow and water-soluble complex with maximum absorption at 380 nm. A smartphone camera and a portable apparatus built for internal lighting control were put together to acquire digital images of reaction mixtures. Digital image processing through the RGB approach was used to establish a quantitative relationship between color intensity and captopril concentration. Under the most suitable operational and experimental conditions, an analytical curve was built monitoring the Blue channel within the concentration range of 3.12 × 10^-5 to 1.21 × 10^-3 mol L^-1. Limits of detection and quantification were equal to 8.06 × 10^-6 and 2.69 × 10^-5 mol L^-1, respectively. Recovery percentage in synthetic urine samples ranged from 97.1% to 102.9%. Results were compared with a reference method and no significant differences were detected at the 95% confidence level. The developed method presents budgetary and environmental advantages concerning the use of cheap and easy-handled devices and the consumption of very low volumes of reagent (800 μL per determination). It can be a useful analytical tool for laboratories with limited financial resources while abiding by green chemistry principles.

Flow-injection spectrophotometric determination of captopril in pharmaceutical formulations using a new solid-phase reactor containing AgSCN immobilized in a polyurethane resin

A simple flow-injection analysis procedure was developed for determining captopril in pharmaceutical formulations employing a novel solid-phase reactor containing silver thiocyanate immobilized in a castor oil derivative polyurethane resin. The method was based on silver mercaptide formation between the captopril and Ag(I) in the solid-phase reactor. During such a reaction, the SCN- anion was released and reacted with Fe3+, which generated the FeSCN2+ complex that was continuously monitored at 480 nm. The analytical curve was linear in the captopril concentration range from 3.0 × 10-4 mol L-1 to 1.1 × 10-3 mol L-1 with a detection limit of 8.0 × 10-5 mol L-1. Recoveries between 97.5% and 103% and a relative standard deviation of 2% for a solution containing 6.0 × 10-4 mol L-1 captopril (n = 12) were obtained. The sample throughput was 40 h-1 and the results obtained for captopril in pharmaceutical formulations using this procedure and those obtained using a pharmacopoeia procedure were in agreement at a 95% confidence level.