A novel, simple and sensitive electrochemical method for the determination of ledipasvir (LED), the
newly FDA approved Hepatitis C antiviral drug was developed and validated using ε-MnO2-modified
graphite electrode. Two different MnO2 polymorphs (g- and ε-MnO2 nanoparticles) were synthesized
and characterized using X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), energy
dispersive X-ray (EDX) and thermogravimetric analysis (TGA). Surface area measurements show that
ε-MnO2 NPs have large surface area of 345 m2
/g, which is extremely high if compared to that of g-MnO2
NPs (38 m2
/g). In addition, a comprehensive study of the difference in the electrochemical behavior of
LED while using pencil graphite electrode (PGE) modified with either g- or ε-MnO2 NPs is carried out. It
was found that surface area and percentage of surface hydroxyls of MnO2 NPs are the key factors governing
the sensitivity of the fabricated electrode toward the oxidation of the positively charged LED.
Scanning electron microscopy (SEM) was employed to investigate the morphological shape of MnO2 NPs
and the surface of the bare and modified electrodes. Moreover, cyclic voltammetry and electrochemical
impedance spectroscopy (EIS) were used for the surface analysis of the modified electrodes. Based on the
obtained results, ε-MnO2/PGE was applied as a selective and sensitive electrode for determination of LED.
Under the optimized experimental conditions, ε-MnO2/PGE provides a linear response over the concentration
range of 0.025e3.60 mmol L1 LED with a low limit of detection, which was found to be
5.10 nmol L1 (4.50 ng mL1
) for the 1st peak and 9.20 nmol L1 (8.10 ng mL1
) for the 2nd one. In addition,
the oxidation behavior of LED is discussed with a full investigation of the oxidized product using FT-