Electron paramagnetic resonance monitoring for on-demand electrochemically-generated radicals

An in-situ electrochemical-electron paramagnetic resonance (EC-EPR) spectroscopy techniques utilizing a new inexpensive and disposable two-electrode system cell was developed. The EC-EPR cell provided maximal sensitivity, minimal dielectric loss along the central axis of the EPR cavity, and was easy handled/mounted without the need for additional adjustments. The developed method was utilized for the analytical determination of ketoconazole (KTZ). The process relied on monitoring the peak-to-peak EPR signal intensities obtained from KTZ radical species that were generated electrochemically at disposable graphite pencil electrode (GPE) surfaces. Optimization of the EC-EPR parameters enabled KTZ radical detection at a concentration and with a volume that were one order of magnitude lower than the corresponding concentrations and volumes tested using chemical oxidation analysis techniques. Moreover, 'on-demand' radical formation was achieved by alternating the applied potentials between the 'ON' and 'OFF' that was used to explore the kinetic of the KTZ-oxidation and its oxidative products.