Electrosynthesis and electrochemical characteristics of 2,2′-(4,5-dihydroxy-3-methoxy-1,2-phenylene)bis(3-oxo-3-phenylpropanenitrile): application as a mediator for determination of hydroxylamine at a carbon nanotube modified electrode surface

Abstract

Electrosynthesis and electrochemical characteristics of an electrodeposited 2,2′-(4,5-dihydroxy-3-methoxy-1,2-phenylene)bis(3-oxo-3-phenylpropanenitrile), DMPP, film on a multi-wall carbon nanotube modified glassy carbon electrode (DMPP-MWCNT-GCE) and its role as a mediator for electrocatalytic oxidation of hydroxylamine are described. Cyclic voltammograms of the DMPP-MWCNT-GCE indicate a pair of well-defined and quasireversible redox couples with surface confined characteristics in a wide pH range of 2.0–12.0. The charge transfer coefficient, α, and the charge transfer rate constant, k_s, of DMPP-MWCNT were calculated to be 0.51 and 10.7 ± 1.7 s⁻¹, respectively. The DMPP-MWCNT-GCE shows a dramatic increase in the peak current and a decrease in the overvoltage of hydroxylamine electrooxidation in comparison with that seen at a bare or MWCNT modified glassy carbon electrode. The kinetic parameters of electron transfer coefficient, α, heterogeneous electron transfer rate constant, k′, and exchange current density, j₀, for the oxidation of hydroxylamine at the modified electrode surface were determined using cyclic voltammetry. Differential pulse voltammetry (DPV) exhibits two linear dynamic ranges 1.0–10.0 μmol L⁻¹ and 10.0–300.0 μmol L⁻¹ as well as a detection limit of 0.37 μmol L⁻¹ for hydroxylamine determination. Finally, the modified electrode was successfully used for the determination of spiked hydroxylamine in a tap water sample.