DFT study and determination of metronidazole based on ionic liquid mediatedcarbon nanotube modified carbon paste electrode

In this work, we prepared a new high sensitive sensor for metronidazole (MNZ) by Single-walledcarbon nanotube (SWCNT) and ionic liquid (IL). The use of SWCNT-IL nano composite in thepaste increased the response of the electrode, significantly. The performance of the proposedcarbon paste electrode was investigated by differential pulse voltammetry (DPV). The sensorprepared based on methods that have been previously reported [1-3]. Various factors such aselectrode composition, types of supporting electrolyte, pH, stirring rate, scan rate were studiedand optimized. The best performance of the electrode was obtained with composition of 76 %graphite powder, 20% ionic liquid and 4% SWCNT. In the optimum experimental conditions(pH=7 Britton-Robinson (B-R) buffer, stirring rate = 400 rpm, scan rate= 50 mV/s) , the currentresponse of the electrochemical sensor studied for metronidazole solution and linearity wasobtained in the range from 5.00 × 10-5 to 5.00 × 10-3mgL-1, with the detection limit of 1.238 × 10-5 mgL-1. The interference study was performed for some drugs and cations that do not show anysignificant interference. This method was successfully applied to the analysis of MNZ inthe milk and egg samples with acceptable recoveries of 90.33–108.0% with RSD ≈ 4.41 %.Also, the non-covalent interactions of the metronidazole with the SWCNT in four differentmanners were investigated by using the density functional theory (DFT) Methods[4] with theM062X and B3LYP functional. Geometries of the investigated species were fully optimized at 6-31+G (d, p) basis sets and Polarizable-Continuum Model (PCM)[5] for investigation of solutesolventinteractions in aqueous solution. The order of the DFT-calculated binding energy of theoptimized geometries is SD2 > SD1> SD3> SD4. The most stable form (SD2) of them involves theinteraction of the Metronidazole with the SWCNT via the nitrogen atom of the nitro group.(Fig.1) that confirms catalytic reduction nitro group in experimental study[6, 7].

Keywords:

Carbon paste electrode , Metronidazole , Differential pulse voltammetry , Single-walledcarbon nanotube , Density functional theory , Ionic liquid