Simultaneous determination of methotrexate and calcium folinate with electrochemical method based on a poly-ABSA/functionalized MWNTs composite film modified electrode

• Preparing positively charged MWNTs with quaternary amine functionalization.
• Fabricating poly-ABSA/MWNTs composite film modified electrode as voltammetric sensor.
• Simultaneous determination of methotrexate and calcium folinate.

A highly sensitive electrochemical sensor was fabricated by electropolymerizing p-aminobenzene sulfonic acid (ABSA) on quaternary amine functionalized multi-wall carbon nanotubes (Q-MWNTs) modified glassy carbon electrode (GCE). Q-MWNTs provide a conductive and stable network for the poly-ABSA (PABSA) immobilization. The voltammetric behaviors of methotrexate (MTX) and calcium folinate (CF) at the PABSA/Q-MWNTs/GCE were investigated by cyclic voltammetry (CV). Compared with bare GCE, Q-MWNTs/GCE and PABSA/GCE, the PABSA/Q-MWNTs/GCE exhibited excellent electrocatalytic oxidation toward MTX and CF. Separation of the oxidation peak potentials for MTX and CF was 0.26 V in phosphate buffer solution (pH 7.0), which made it suitable for simultaneous determination of these two compounds by differential pulse voltammetry (DPV). Under the optimized conditions, the anodic peak current of MTX was linear with the concentration from 0.1 to 8.0 μM in the presence of 8.0 μM CF, with a detection limit of 0.015 μM (S/N = 3). At the same time, the anodic current of CF was linear with the concentration from 0.1 to 6.5 μM with a detection limit of 0.020 μM in the presence of 8.0 μM MTX. The proposed sensor showed advantages of simple preparation, high sensitivity, good reproducibility and stability. It was successfully applied to simultaneous determination of MTX and CF in urine samples.

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