Electroanalysis of metronidazole using exfoliated MoS2 sheets and electrodeposited amorphous MoSx

Abstract

Molybdenum disulfide, MoS2, sheets were obtained by exfoliation of the bulk powders in an aqueous solution containing 1.0 mM tryptophan and then drop-cast onto a glassy carbon electrode to give GCE/MoS2. For comparative purposes, amorphous MoSx was electrodeposited directly onto the glassy carbon electrode from a 5 mM (NH4)2MoS4 solution. Both electrodes were employed in the electrochemical detection of the antibiotic metronidazole (MTZ). While the MTZ was reduced at both modified surfaces, the GCE/MoS2 was superior and this was attributed to a higher surface area, a lower charge-transfer resistance and to the presence of edges and defects in the sheets that facilitate the electron transfer reaction.Using differential pulse voltammetry, impressive linear calibration curves were obtained for GCE/MoS2 extending from 1.9 to 2000 μM and from 40 to 1990 nM at the lower concentrations. A high sensitivity of 13.32 μA μM–1 cm–2 and a LOD value of 4.3 nM were obtained using the lower concentration linear range. Good selectivity was achieved in the presence of interferents typically found in aquatic environments, with acceptable repeatability, good stability over a 7-day period and good recovery (88.7 ± 3.9%) in water samples taken from a river.