A portable solid-state electrochemical sensor based on N-doped graphite as a transducer layer for determination of a multiple sclerosis managing medication in biological fluids

Solid-state electrochemical sensors have shown tremendous promise for portable and reliable ion detection, thanks to implementing new functional materials as ion-to-electron transducer and innovative designs. Herein, a portable, disposable, and eco-friendly solid-state electrochemical sensor was established for the selective sensing of dalfampridine (FAM) in different matrices. The fabricated sensor is based on utilizing N-doped graphite as an intermediate transducer layer between calix[6]arene-doped PVC ion-sensing membrane and a screen-printed electrode. This is the first time N-doped graphite material is utilized in fabricating ion-selective electrode sensors. In-house synthesis of N-doped graphite was accomplished by soft nitriding of graphite with urea. Then it was characterized using both X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR). The electrochemical performance of the developed sensor was assessed and compared to a transducer-free sensor. A significantly enhanced electrode performance: detection limit of 5.98 x 10(-6) mol L-1, rapid response time of 10 s, and reduced potential drift, was observed. The proposed sensor exhibits a Nernestian potentiometric slope of 59.19 mV/decade over a linear response range of 8.0 x 10(-6) to 1.0 x 10(-2) mol L-1. The proposed sensor has been efficaciously employed for selective potentiometric determination of FAM in its pure form, pharmaceutical formulation, and in different biological fluids (plasma, urine, and human milk) without any prior sample treatment steps. Finally, analytical method greenness was assessed using Eco-scale as well as Green Analytical Procedure Index (GAPI) approaches.