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 x 10(-6) and 8.0 x 10(-5) M with the detection limit of 2.14 x 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 pK(a) 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 pK(a) 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. (C) 2013 Elsevier B.V. All rights reserved.