Selective Electroanalytical Method for the Determination of Roxarsone in Poultry Feed and Litter

Electrochemical determination of Roxarsone using preconcentration-based signal amplification on modified screen-printed electrode

A lab-made screen-printed electrode based on poly(ethylene terephthalate) (PET) substrate modified with a hybrid film containing gold nanoparticles-decorated graphene (AuNPs-GRA/PET-SPE) was employed for the voltammetric determination of Roxarsone (ROX) in chicken purge and river water samples. The electrode exhibited an increased electroactive area and enhanced charge transfer due to the nanostructured matrix. The electrochemical determination involved a preconcentration approach with a reduction step of ROX at a constant potential of -0.6 V, followed by voltammetric sweep towards the oxidation of the adsorbed hydroxylamine at 0.32 V. The methodology achieved a limit of detection of 60 nM and 97 nM for ROX in diluted river water and chicken purge samples, respectively. This effective methodology offers a promising tool for monitoring ROX levels in environmental and food samples.

Diclofenac-Impregnated Mesoporous Carbon-Based Electrode Material for the Analysis of the Arsenic Drug Roxarsone

This paper describes a novel electrode material, diclofenac-impregnated mesoporous carbon modified with a cationic surfactant, cetyltrimethylammonium bromide (DF-CMK-3/CTAB), for ultratrace analysis of the arsenic drug roxarsone (ROX). DF-CMK-3 amorphous carbon is a material with a high specific surface area and well-defined, hexagonally ordered, thin mesopores. The functional groups attached to the carbonaceous surface, such as chromene and pyron-like oxygen groups, lactam, and aromatic carbon rings, have the basic character and they can donate electrons. Modification of DF-CMK-3 with a CTAB layer significantly increases the analytical signal due to electrostatic interactions between the cationic surfactant and the anion form of ROX in the acidic medium. The voltammetric procedure at the glassy carbon sensor modified with DF-CMK-3/CTAB exhibited excellent sensitivity (limit of detection of 9.6 × 10-11 M) with a wide range of linearity from 5.0 × 10-10 to 1.0 × 10-4 M. Analysis of real samples (treated municipal wastewater and river water) showed recoveries from 96 to 102% without applying the complicated sample pretreatment step. The sensor demonstrated excellent sensitivity in the analysis of the arsenic drug ROX in the presence of interferences in environmental water samples.

Glassy Carbon Modified with Cationic Surfactant (GCE/CTAB) as Electrode Material for Fast and Simple Analysis of the Arsenic Drug Roxarsone

For the fast and simple sensing of the arsenic drug roxarsone (ROX), the development of a glassy carbon electrode (GCE) modified with cationic surfactant (cetyltrimethylammonium bromide, CTAB) material is critical. The CTAB-modified glassy carbon electrode, in contrast to the unmodified one, showed excellent behavior for electrochemical reduction of ROX using cyclic voltammetry (CV) and square-wave adsorptive stripping voltammetry (SWAdSV) techniques. CV studies reveal an irreversible reduction process of NO₂ to NH-OH in the ROX molecule in NaAc-HAc buffer (pH = 5.6). The electrode material was characterized using CV and electrochemical impedance spectroscopy. The experiments show that the surfactant-modified material has faster electron transfer and a higher active surface area, and permits a diffusion-adsorption-controlled process. After optimization, the SWAdSV procedure with GCE/CTAB has linear ranges of 0.001-0.02 and 0.02-20 µM, and a detection limit of 0.13 nM. Furthermore, the procedure successfully determined roxarsone in river water samples.

Development of robust multifunctional CrNiCo-P/GCN catalyst for oxygen evolution reaction, electrochemical sensing, and photodegradation of roxarsone

In this study, we designed a CrNiCo-P/GCN composite for use as a high-performance multifunctional catalyst for the oxygen evolution reaction (OER), electrochemical determination, and photodegradation of roxarsone (ROX). CrNiCo-P/GCN demonstrates favorable charge resistance and electrical conductance due to its intrinsic properties. It exhibits an admirable OER overpotential of 290 mV with a lower Tafel plot value of 125 mV dec^-1 in alkaline media and compared with the control samples. Furthermore, this composite also demonstrates high performance in electrochemical sensing of ROX over a wide concentration range of 1-413 μM with a lower limit of detection (LOD) of 31 nM in phosphate buffer. Moreover, this composite is a promising electrocatalyst for ROX sensors in practical analysis and also possesses excellent photodegradation of ROX under visible light irradiation.

A Highly Selective and Sensitive Fluorescent Sensor Based on Molecularly Imprinted Polymer-Functionalized Mn-Doped ZnS Quantum Dots for Detection of Roxarsone in Feeds

Roxarsone (ROX) as an organoarsenic feed additive has been widely used in livestock breeding and poultry industry, but ROX can degrade into highly toxic inorganic arsenic species in natural environments to threaten to the environment and human health. Therefore, there is a considerable interest in developing convenient, selective and sensitive methods for the detection of ROX in livestock breeding and poultry industry. In this work, a fluorescent molecularly imprinted polymer (MIPs) probe based on amino-modified Mn-ZnS quantum dots (QDs) has been developed by sol-gel polymerization for specific recognition of ROX. The synthesized MIPs-coated Mn-ZnS QDs (MIPs@Mn-ZnS QDs) have highly selective recognition sites to ROX because there are multi-interactions among the template ROX, functional monomer phenyltrimethoxysilane and the amino-functionalized QDs such as the π-π conjugating effect, hydrogen bonds. Under the optimal conditions, an obvious fluorescence quenching was observed when ROX was added to the solution, and the quenching mechanism could be explained as the photo-induced electron transfer. The MIPs@Mn-ZnS QDs sensor exhibited sensitive response to ROX in the linear range from 3.75 × 10^-8 M to 6.25 × 10^-7 M (R² = 0.9985) and the limit of detection down to 4.34 nM. Moreover, the fluorescence probe has been applied to the quantitative detection of ROX in feed samples, and the recovery was in the range of 91.9% to 108.0%. The work demonstrated that the prepared MIPs@Mn-ZnS QDs probe has a good potential for rapid and sensitive determination of ROX in complicated samples.

A disposable molecularly imprinted electrochemical sensor for the ultra-trace detection of the organophosphorus insecticide phosalone employing monodisperse Pt-doped UiO-66 for signal amplification

In this work, a disposable molecularly imprinted electrochemical sensor was developed towards the highly sensitive and selective detection of the organophosphorus insecticide phosalone (PAS), employing a home-made carbon paste microelectrode (CPME) modified with a Zr-based metal-organic framework catalyst (Pt-UiO-66) and a mesoporous structured conductive molecularly imprinted polymer (MIP). Pt-UiO-66 octahedra with isolated dispersed Pt nanoparticle active sites were firstly incorporated into the CPME to provide a remarkably amplified signal for voltammetric determination. The mesoporous MIP was then synthesized onto the Pt-UiO-66/CPME via electropolymerization and a subsequent sol-gel process, which could bind the PAS template molecules through hydrogen bond, coordinate bonding, hydrophobic interaction, and π-π stacking interaction. Morphological, structural, and electrochemical characterization studies revealed that this nano-sized MIP provided excellent features for PAS detection, including high porosity, large surface area, enhanced electron-transport ability, greatly improved diffusion capacity, and strong recognition specificity. Therefore, the resulting sensor exhibited an outstanding linearly proportional concentration domain of 0.50 nM-20 μM, low detection limit of 0.078 nM, marked selectivity over certain interferences with similar configurations, considerable repeatability, reproducibility, and stability for the analysis of PAS. Moreover, the sensor was successfully applied for the determination of PAS in agricultural products and environmental samples with results in good compatibility with a chromatographic method, indicative of the high reliability and practicability. Such an electrochemical sensor might open a novel window for the investigation of selective sensing of small organic species from their analogues coupled with the molecular imprinting technique.