In-situ tailoring of the electrocatalytic properties of screen-printed graphite electrodes with sparked generated molybdenum nanoparticles for the simultaneous voltammetric determination of sunset yellow and tartrazine

This work describes the development of a "green" electrocatalytic surface based on molybdenum-sparked screen-printed graphite electrodes (sparked Mo-SPEs) for the voltammetric determination of azo synthetic colorants. Sparked Mo-SPEs were produced by an in-situ, liquid-free metal-to-SPE electric discharge approach at 1.2 kV under atmospheric conditions. Morphological studies with scanning electron microscopy and energy dispersive X-ray spectroscopy revealed the formation of Mo nanoparticles that have been evenly distributed over the entire surface of the electrodes. X-ray photoelectron spectroscopy showed that the atomic percentage of Mo over the electrode surface is only 0.5 +/- 0.1% in the form of metallic Mo (25.3%) and Mo(VI) (74.7%). In 0.1M acetate buffer solution, pH 5 sparked Mo-SPEs exhibited well-defined oxidation peaks at 0.730 V for sunset yellow (SY) and 0.973 V for tartrazine (TAR) versus Ag/AgCl/3M KCl. Sparked Mo-SPE demonstrated remarkably increased responses compared with plain or electrodeposited MoxOy modified-graphite SPEs and enabled the simultaneous determination of the targets in the nano molar range. Under selected experimental variables a linear calibration curve over the concentration range from 5 to 250 nM SY/TAR was constructed. The limits of detection (S/N 3) were 2 nM. The response of Mo-SPE in the presence of other azo colorants was also investigated. The developed electrodes were successfully applied to the determination of SY and TAR in real-world samples. The accuracy of the method was established by recovery studies. Recovery was between 94-109%.