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 −3  mol/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 −2  mol/L). The dissolution method was developed according to FDA regulations using USP apparatus I, 75 rpm rotation speed, at 37.0 ± 0.5 °C and 1000 ml of water, pH 3.0 (adjusted with 2.0 N HCl) as the dissolution medium. Dissolution profiles were generated over 24 h 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.