Determination of Methotrexate Using an Electrochemical Sensor Based on Carbon Paste Electrode Modified with NiO Nanosheets and Ionic Liquid

In this paper, the application of NiO nanosheets (NiO NSs) for the detection of methotrexate (MTX) is described. The NiO NSs were synthesized using a hydrothermal method. The electrocatalytic activity of two modifiers, ionic liquid (IL) and NiO NSs, was examined on a carbon paste electrode (CPE) in relation to MTX, utilizing voltammetry methods such as cyclic voltammetry (CV), linear sweep voltammetry (LSV), differential pulse voltammetry (DPV), and chronoamperometry at 0.1 M phosphate buffer solution (PBS) pH = 7.0. The anodic peak currents for MTX on the NiO NSs/IL/CPE were approximately 3.5 times greater than those on unmodified CPE. Based on DPV measurements, the electrochemical sensor demonstrated a linear response in the concentration range (LDR: 0.01 µM to 160.0 µM), with a limit of detection (LOD: 0.003 µM). Moreover, the NiO NSs/IL/CPE sensor demonstrated good stability, repeatability, reproducibility, and selectivity, which were of importance in the electroanalysis of compounds. Lastly, the practicality of the NiO NSs/IL/CPE sensor was assessed by analyzing MTX levels in urine samples and pharmaceutical formulation, yielding satisfactory recovery rates of 97.1% to 103.3%.