Differential pulse adsorptive stripping voltammetric determination of methotrexate using a functionalized carbon nanotubes-modified glassy carbon electrode

A glassy carbon electrode (GC) containing multiwalled functionalized carbon nanotubes (MWCNTs) immobilized within a dihexadecylhydrogenphosphate film (DHP) is proposed as a nanostructured platform for determination of methotrexate (MTX) concentration (a drug used in cancer treatment) using differential pulse adsorptive stripping voltammetry (DPAdSV). The voltammograms for a MTX solution using MWCNTs-DHP/GC electrode presented an oxidation peak potential at 0.98 V vs. Ag/AgCl (3.0 mol L-1 KCl) in a 0.1 mol L-1 sulphuric acid. The apparent heterogeneous electron transfer rate constant of 0.46 s(-1) was calculated. The recovery area of 2.62 x 10(-9) mol cm(2) was also obtained. Under the optimal experimental conditions, the analytical curve was linear in the MTX concentration range from 5.0 x 10(-8) to 5.0 x 10(-6) mol L-1, with a detection limit of 3.3 x 10(-8) mol L-1. The MWCNTs-DHP/GC electrode can be easily prepared and was applied for the determination of MTX in pharmaceutical formulations, with results similar to those obtained using a high-performance liquid chromatography comparative method.