DESIGNING A FLOW INJECTION SYSTEM FOR THE DETERMINATION OF CAPTOPRIL DRUG USING DTNB

Abstract

The stopped-flow injection technique is a simple analytical method with many applications, especially in chemical analysis based on the physical and chemical treatment of a diluted sample injected into the carrier stream. Its speed and high accuracy characterizes the technique and is cost-effective as it does not require high concentrations and large volumes of the substance to be estimated and the reagent used. Furthermore, it is an environmentally friendly technology, considered one of the most important chemical analysis techniques, including the determination of drugs in pharmaceutical preparations.

Captopril is a medication that includes L-proline, which enhances its bioavailability when taken orally. It has multiple applications, including treating high blood pressure, heart disease, and diabetic nephropathy, as well as preserving kidney function. Additionally, it has been used as an antidepressant.

In this technique, captopril is reacted with DTNB reagent in the presence of buffer solution (Na2HPO4) to produce a yellow product with a wavelength of 421 nm. The reaction is carried out under certain physical and chemical conditions, such as a flow rate of 1.0 ml/min, a reaction coil length of 100 cm, and a reaction time of 20 seconds. The technique can detect drug concentrations within the range of 1-200 ppm, with a limit of detection (LOD) and limit of quantitation (LOQ) of 0.22 ppm and 0.764 ppm, respectively. The technique has a relative standard deviation (RSD) 568 and a correlation coefficient (R2) 0.9984.