Electrocatalytic oxidation of hydroxylamine at Ni(II)-morin complex modified carbon nanotube paste electrode

A Voltammetric Sensor for the Determination of Hydroxylamine Using a Polypyrrole Nanotubes-Modified Electrode

In this work, we develop an electrochemical sensor using a polypyrrole nanotubes-modified graphite screen-printed electrode (PPy NTs/GSPE) for sensing hydroxylamine. The PPy NTs/GSPE-supported sensor has an appreciable electrocatalytic performance and great stability for hydroxylamine oxidation. Compared to a bare graphite screen-printed electrode, we demonstrate that using the PPy NTs/GSPE leads to a significant reduction in the oxidation potential of hydroxylamine. The standard curve shows a linear relationship ranging from 0.005 to 290.0 μM (R2  =  0.9998), with a high sensitivity (0.1349 μA/μM) and a narrow limit of detection (LOD) of 0.001 μM. In addition, the PPy NTs/GSPE has satisfactory outcomes for hydroxylamine detection in real specimens.

Fabrication of Highly Sensitive and Stable Hydroxylamine Electrochemical Sensor Based on Gold Nanoparticles and Metal-Metalloporphyrin Framework Modified Electrode

This paper describes the immobilization of gold nanoparticles on metal-metalloporphyrin frameworks (AuNPs/MMPF-6(Fe)) through electrostatic adsorption. The composites were characterized by powder X-ray diffraction, zeta potential, transmission electron microscopy, electrochemical impedance spectroscopy, and voltammetric methods. MMPF-6(Fe) exhibited a pair of redox peaks of the Fe(III)TCPP/Fe(II)TCPP redox couple. The AuNPs/MMPF-6(Fe)-based electrochemical sensor demonstrates a distinctly higher electrocatalytic response to the oxidation of hydroxylamine due to the synergic effect of the gold metal nanoparticles and metal-metalloporphyrin matrix. The voltammetric current response exhibits two linear dynamic ranges, 0.01-1.0 and 1.0-20.0 μmol L(-1), and the detection limit was as low as 0.004 μmol L(-1) (S/N = 3). Moreover, the biosensor exhibits high reproducibility and stability in acid solution. Our work not only offers a simple way to achieve the direct electrochemical behavior of metalloporphyrin but also expands the potential applications of MOFs-based composites in bioanalysis.

A new strategy for determination of hydroxylamine and phenol in water and waste water samples using modified nanosensor

A carbon paste electrode modified with p-chloranil and carbon nanotubes was used for the sensitive and selective voltammetric determination of hydroxylamine (HX) and phenol (PL). The oxidation of HX at the modified electrode was investigated by cyclic voltammetry (CV), chronoamperommetry, and electrochemical impedance spectroscopy. The values of the catalytic rate constant (k), and diffusion coefficient (D) for HX were calculated. Square wave voltammetric peaks current of HX and PL increased linearly with their concentrations at the ranges of 0.1-172.0 and 5.0-512.0 μmol L(-1), respectively. The detection limits for HX and PL were 0.08 and 2.0 μmol L(-1), respectively. The separation of the anodic peak potentials of HX and PL reached to 0.65 V, using square wave voltammetry. The proposed sensor was successfully applied for the determination of HX and PL in water and wastewater samples.

Modified carbon nanotube paste electrode for voltammetric determination of carbidopa, folic Acid, and tryptophan

A simple and convenient method is described for voltammetric determination of carbidopa (CD), based on its electrochemical oxidation at a modified multiwall carbon nanotube paste electrode. Under optimized conditions, the proposed method exhibited acceptable analytical performances in terms of linearity (over the concentration range from 0.1 to 700.0 μM), detection limit (65.0 nM), and reproducibility (RSD = 2.5%) for a solution containing CD. Also, square wave voltammetry (SWV) was used for simultaneous determination of CD, folic acid (FA), and tryptophan (TRP) at the modified electrode. To further validate its possible application, the method was used for the quantification of CD, FA, and TRP in urine samples.