In-line potentiometric monitoring of dissolution behavior of verapamil hydrochloride versus traditional pharmacopeial method: A comparative study

Abstract

The possibility of obtaining analytical signals without sample pre-treatment or derivatization is the most environmentally friendly method of analysis. In this work a comparison between potentiometric methods and traditional spectrophotometric and HPLC methods for monitoring of dissolution of drugs was established. As an example, an electro-analytical procedure was developed and validated for studying the dissolution of sustained release capsules containing verapamil hydrochloride (VER) by in-line potentiometric measurement system without sample pre-treatment. A sensor was fabricated for determination of VER in its dissolution medium using a poly(vinyl chloride) (PVC) based membrane and tetraphenylborate (TPB) as a cation exchanger. Nitrophenyl octyl ether (NPOE) was used as a plasticizer. The ion pair was obtained in situ by soaking the PVC membranes in 1×10−3mol/L VER solution. The sensor was validated according to the IUPAC recommendations. The proposed sensor showed fast, stable near Nernstian responses across a relatively wide VER concentration range (4×10−5 to 1×10 −2mol/L). The dissolution method was developed according to FDA regulations using USP apparatus I, 75rpm rotation speed, at 37.0±0.5°C and 1000ml of water, pH 3.0 (adjusted with 2.0N HCl) as the dissolution medium. Dissolution profiles were generated over 24h and compared to those obtained by the official spectrophotometric method. The transpose of a Nikolskii–Eisenman type function performed the conversion of potential to percentage of dissolution. The proposed sensor can be used as bench-top real-time analyzer for in-process tracking of the concentration of VER in monitoring its dissolution and in its pharmaceutical dosage forms. The proposed method was validated and it is considered to be a green eco-friendly technique that neither require sample pre-treatment nor consume any solvents.