Electroanalytic investigation of some drugs used in cancer chemotherapy by voltammetric method

Vinca alkaloids have been used in the treatment of human cancers for more than 40 years. In this study, a novel application of single-use pencil graphite (PG) electrode is introduced for the determination of Vinorelbine, one of the semisynthetic derivatives of Vinca alkaloids. The electrochemical oxidation of Vinorelbine was first investigated by cyclic voltammetry using this electrode in aqueous solutions. Special attention was given to the use of adsorptive stripping voltammetry at a surface of PG electrode and glassy carbon (GC) one (for comparison purpose) in aqueous solutions over the pH range of 2.0-12.0 both with and without the addition of surfactants. The sensitivity of the stripping voltammetric measurements was significantly improved when the anionic (sodium dodecylsulfate, SDS) and cationic (tetra-n-butylammonium bromide, TBAB) surfactants were present in the Vinorelbine-containing electrolyte solution at pH 2.0-4.0 and pH 9.0-10.0, respectively, by using PG electrode. Using square-wave stripping mode, Vinorelbine yielded a well-defined voltammetric response in Britton-Robinson buffer pH 10.0 containing 3×10-3 M TBAB at +0.75 V (vs. Ag/AgCl) (after 120 s accumulation at +0.0 V). The process could be used to determine this compound in the concentration range of 2.3×10-8 – 5.8×10-6 M, with a detection limit of 7.5×10-9 M (base-5.8 ng mL-1). The proposed method was successfully applied to pharmaceutical formulations and the spiked human urine samples.