Electrochemical preparation of sodium dodecylsulfate doped over-oxidized polypyrrole/multi-walled carbon nanotube composite on glassy carbon electrode and its application on sensitive and selective determination of anticancer drug: pemetrexed.

Electrochemical oxidation of pemetrexed (PMX) was studied on bare, carboxylic acid functionalized multi-walled carbon nanotubes and over-oxidized polypyrrole modified (oo-PPy/MWCNTs-COOH/GCE) glassy carbon electrodes by cyclic and adsorptive stripping differential pulse voltammetric techniques. The oo-PPy/MWCNTs-COOH/GCE is very sensitive to the oxidation of PMX. The results proved that the over-oxidation of the PPy film gave a negative charge density on porous layer that improved the adsorption for PMX. The effects of pH, concentrations of MWCNTs and monomer, the number of cycles for the electropolymerization and the scan rate for sensor preparation were optimized. The MWCNTs-COOH and oo-PPy based sensor showed an excellent recognition capacity toward PMX. The linear responses have been obtained in the range from 8.00 × 10(-7)M to 1.00 × 10(-4)M with 2.04 × 10(-7)M detection limit for the bare GCE and from 1.00 × 10(-8)M to 1.00 × 10(-7)M with 3.28 × 10(-9)M detection limit for the modified GCE. The oxidation of PMX was controlled by the adsorption process on both types of electrode surfaces. The proposed methods were compared with the literature on UV spectrophotometric assay, which was carried out at an absorption maximum of 225 nm. The proposed method and the designed sensors have been successfully applied for the determination of PMX in pharmaceuticals.

Analytical application of polymethylene blue-multiwalled carbon nanotubes modified glassy carbon electrode on anticancer drug irinotecan and determination of its ionization constant value.

The voltammetric behavior of anticancer drug irinotecan (IRT) was investigated at poly (methylene blue)/multi-walled carbon nanotube (PMB/MWCNT) modified glassy carbon electrode (GCE). The modified electrode surface was characterized by a scanning electron microscope (SEM). The PMB/MWCNT modified GCE exhibits a distinct shift of the oxidation potential of IRT on the cathodic direction and a considerable enhancement of the peak current compared with bare electrode. The calibration curve was linear between the concentration range 8.0 × 10(-6) and 8.0 × 10(-5)M with the detection limit of 2.14 × 10(-7)M by differential pulse voltammetry in pH 10.0 Britton-Robinson buffer solution. Controlled potential coulometry was applied to find transferred electron numbers due to the oxidation of IRT. In this study, the pKa value of IRT was also determined by the dependence of the retention factor on the pH of the mobile phase. The effect of the mobile phase composition on the ionization constant was studied by measuring the pKa at different acetonitrile-water mixtures, ranging between 35 and 50% (v/v) using the reversed-phase liquid chromatography (RP-LC) method with UV detector. IRT was exposed to thermal, photolytic, hydrolytic and oxidative stress conditions, and the stressed samples were detected by the proposed method. Sensitive, rapid, and fully validated electrochemical and RP-LC methods for the determination of IRT in its dosage form were presented in details.