Development of a sensitive voltammetric sensor for diltiazem determination in biological samples using MWCNT/PPy-PBA modified glassy carbon electrode

A glassy carbon (GC) electrode was modified for diltiazem determination in various samples using the cyclic voltammetry (CV) method. The modification consists of coating a multi-walled carbon nanotubes (MWCNTs) layer on the GC electrode, which is followed by electro-polymerization of pyrrole in the presence of phenylboronic acid (PBA). The experimental design was used to find optimum experimental conditions for electrode fabrication and diltiazem determination. Under optimum conditions, the calibration curve of diltiazem is linear in 0.25–2 μmol/L and 2–80 μmol/L ranges with a detection limit of (LOD) 7.1 × 10−8 mol/L. Further application of the GC/MWCNT/PPy-PBA electrochemical sensor for diltiazem determination shows good reproducibility, high sensitivity, and reasonable selectivity with no major interference. These characteristics make the sensor suitable for the determination of diltiazem in biological and pharmaceutical samples. To rationalize the modification on the electrochemical behavior of the sensor regarding diltiazem, geometrical interaction and interaction energy of the analyte with the sensor surface were investigated using highly accurate quantum mechanical methods implemented in Gaussian 09 software. The calculations fully confirm experimental evidence.