Voltammetric behaviour of antimalarial drug artesunate in solubilized systems

Voltammetric methods for electrochemical characterization and quantification of artemether-based antimalarials

Every year substandard and falsified (SF) artemisinin derivative-based antimalarials are responsible for the loss of 450 000 deaths and billions of GBP. The lack of infrastructure and funds to support pharmaceutical quality control in many low-and-middle-income countries contributes to this problem. This work assesses fitness for purpose of voltammetric methods for identification and quantification of artemether in the presence of excipients. Electrochemical characterization of artemether using cyclic voltammetry shows that the reduction of artemether is chemically irreversible within the potential range of -0.4 V to -1.4 V. A chronocoulometric quantification algorithm for artemether is created and tested with pure artemether, as well as filtered and unfiltered Riamet® tablets. Filtration of Riamet® tablets provides no additional benefit for the quantification of artemether in Riamet®. In addition, artemether's response to pH indicates possible protonation and coupled homogeneous chemistry. Finally, sodium sulfite is an effective means of removing dissolved oxygen and improving artemether signal resolution in air-equilibrated PBS. This concludes that electrochemical analysis is a promising method for artemether identification and quantification.

Synthesis and validation of ultrasensitive stripping voltammetric sensor based on polypyrrole@ZnO/Fe3O4 core-shell nanostructure for picomolar detection of artesunate and dopamine drugs

A stripping voltammetric sensor for ultrasensitive detection of artesunate (ART) and dopamine HCl (DA) has been successfully developed using a Ppy@ZnO/Fe₃O₄ core-shell nanocomposite ([PZM])-modified carbon paste sensor (MCPS). Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, dynamic light scattering, Brunauer-Emmett-Teller surface area method, and high-resolution transmission electron microscopy were used to characterize the physicochemical properties of the nanomaterials. Noteworthily, the morphology of [PZM] reveals a spherical core-shell nanostructure with an increase in the average diameter range of 20-37.5 nm (specific surface area (SSA) of 28.5 m² g^-1 (0.0247 cm³ g^-1)) when compared with the average diameter range 7.5-15.7 nm (SSA of 5.43 m² g^-1 (0.0111 cm³ g^-1)) of ZnO/Fe₃O₄[ZM]. The [PZM] MCPS provided the best electroactive surface area (0.078 cm²) and the least electrocatalytic activity (R_st = 370 Ω). Furthermore, the MCPS showed low detection limits (LODs) of 0.092 pg mL^-1 (0.24 pM) and 0.0046 pg mL^-1 (0.03 pM) for ART and DA, respectively. Moreover, LODs were found to be 0.029 pg mL^-1 (0.75 pM) and 0.014 pg mL^-1 (0.09 pM) for ART mixed with 0.7 pM of DA (ART₁) and DA in the presence of 2.0 pM of ART drug (DA₁), respectively. In addition, the MCPS revealed a proper repeatability, reproducibility, and storage stability (93.5-90.48%). During the routine analysis, the [PZM] MCPS detected ART and DA concentrations in human urine, without interference.

Research progress in electroanalytical techniques for determination of antimalarial drugs in pharmaceutical and biological samples

The review focusses on the role of electroanalytical methods for determination of antimalarial drugs in biological matrices and pharmaceutical formulations with a critical analysis of published voltammetric and potentiometric methods.