Voltammetric Measurements Research Articles

Mercury Detection in Novel Foods by a Smart Pocket Sensor

AbstractMercury is one of the most well‐known toxic contaminants of natural and anthropogenic origin in aquatic ecosystems that can bioaccumulate in vegetal and animal organisms. In this work, we propose a smart detection system for Hg(II) ions by square wave anodic stripping voltammetry at nanocomposite graphite screen‐printed electrodes, as an analytical tool to be applied in food quality control. The nanocomposite surfaces were obtained by the modification of screen‐printed graphite electrodes with poly(l‐aspartic acid) and gold nanoparticles and were characterized by means of electrochemical techniques. An exhaustive study of the experimental conditions involved both in the electropolymerization and in the voltammetric stripping measurements was addressed to develop a reliable method capable of measuring Hg(II) concentration in the low μg/L range, both in conventional and drop configurations. The sensor was integrated in a smart setup, comprising a Sensit Smart pocket instrument connected to a smartphone, thus proving its applicability for in situ analysis due to its cost‐effectiveness. The analytical significance of the developed sensor was assessed by detecting Hg(II) in novel food samples.

Enhancing the electrochemical performance of graphite sheet electrodes for ketamine detection

Flexible graphite sheets (GS) have been a promising material for developing electrochemical sensors. In this work, we showed that the electrochemical activation protocol (+1.4 V followed by -1.0 V vs. Ag|AgCl|KCl(sat.) both at 200 s) in alkaline medium (0.5 mol l-1 NaOH) enhances the electrochemical activity of GS. Before the treatment, cyclic voltammetric profile of inner-sphere [Fe(CN)6]3-/4- redox couple at 50 mV s-1 exhibited an ill-defined voltammetric profile (ΔEp = 800 mV) while an increase in the reversibility was achieved (ΔEp = 225 mV) after the treatment. Additionally, the lower charge transfer resistance (Rct) measured by Electrochemical Impedance Spectroscopy (EIS) and a higher heterogeneous electron transfer constant (k0) corroborate with the enhancement in the electrochemical performance of treated GS electrodes. The SEM images revealed an irregular pattern with number of grooves, indicating a partially surface exfoliation and AFM analysis displayed an increase in the roughness. These findings agreed with the estimation of electroactive area which increased 3-times after the treatment. As proof of concept, ketamine (KET), an anesthetic often used as drug of abuse, was determined in synthetic saliva and veterinary pharmaceutical samples using treated GS electrodes and square wave voltammetric measurements. Linear range of 5.0–100.0 µmol l-1 with a limit of detection value of 2.1 µmol l-1 was obtained for KET. Appropriate recovery values (∼105 %) for the analysis of samples were achieved.

First Voltammetric Determination of Karbutylate via Pencil Graphite, Glassy Carbon, and Boron-Doped Diamond Electrodes in Soil Sample

We investigated the electrochemical behavior of carbamate pesticide-type karbutylate (KB) with boron-doped diamond (BDD), glassy carbon (GC), and pencil graphite (PG) electrode, and analytical determination in real samples. Similar to organophosphate insecticides, carbamate pesticides are produced from carbamic acid and are extensively utilized in agriculture, gardens, and residences. Therefore, a rapid and simple detection of KB in real samples is important. Carbon-based electrodes are widely used in electroanalytical chemistry due to their rich surface chemistry, chemical inertness, broad potential window, low background current, and congruency for various demanding applications. Three different carbon-based electrodes were used. The effect of buffer solutions, scan rate, square wave (SWV), and differential pulse voltammetry parameters on the voltammetric response of KB was tested. The optimum working media for all three electrodes was determined as pH 2.00 phosphate buffer solution and voltammetric measurements were carried out in this media. Under optimum experimental conditions, linear calibration dependences for KB were obtained as 6.00 × 10−7–8.00 × 10−5 M, 4.00 × 10−7–8.00 × 10−5 M, and 8.00 × 10−8–8.00 × 10−5 M with a limit of detection of 2.18 × 10−7, 3.71 × 10−8 M, and 2.66 × 10−8 M by the BDD, GC, and PG electrodes, respectively, using SWV. As a result, sensitive determination of KB has been successfully performed using different carbon-based electrodes in real soil samples.

Non-enzymatic detection of versatile anti-oxidant in diverse media using 3D spinel nickel cobalt oxide with 2D tungsten carbide nanohybrid heterostructure electrocatalyst

Diphenylamine (DPA), an organic amine derivative compound widely used in agriculture and polymer industries as an anti-scaling and anti-oxidising agent. The excessive and prolonged usage of DPA in agricultural products would result in the accumulation of it. The poor degradation ability and associated health hazards marked it as a “contaminant of emerging concern”. Since DPA is not completely banned in many countries, measuring the trace levels of DPA is essential to ensure the safety of the ecosystem. Therefore, the electrochemical sensing method was applied for the precise detection of an infinitesimal concentration of this component. In this work, we have prepared a spinel nickel cobalt oxide with a tungsten carbide (NCO/WC) electrocatalyst-based electrochemical sensor for the accurate detection of DPA. The structural, and morphological details were examined with Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscope (FE-SEM), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analyses. The electrochemical properties were evaluated with impedance and voltammetric measurements. Various voltammetric techniques were utilized to assess the efficiency of NCO/WC towards DPA. Significantly, our sensor displayed a low detection (0.001 µM), and low quantification (0.0048 µM) limits, good linear range (0.01 to 147 µM), optimal sensitivity (1.716 µA µM−1 cm−2), remarkable selectivity, appreciable repeatability, reproducibility, and stability performance outcomes. Then, the sensor was employed to monitor the DPA in various matrices like agricultural, environmental, and human samples and conquered astonishing results. These findings suggest that our NCO/WC-based electrochemical sensor is a promising platform for the enhanced detection of DPA.

Green electrochemical sensor based on ZnO@α-Fe2O3 NPs modified carbon paste electrode for sensitive voltammetric determination of the FDA-approved Anti-COVID-19 medication baricitinib

In this study, we developed an electrochemical sensor for the sensitive voltammetric determination of Baricitinib (BCT), a recently FDA-approved medication for curing COVID-19. Voltammetric measurements were employed using a carbon paste electrode modified with zinc oxide and iron oxide nanoparticles (ZnO/α-Fe2O3-NPs/CPE). The composition of the fabricated electrode was optimized, and the best sensitivity was achieved by utilizing 5% of ZnO/α-Fe2O3-NPs, which maximized the electroactive surface area. The final optimized electrode was electrochemically and physicochemically characterized by exploiting the following techniques: X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). All experimental parameters, including the pH and scan rate, have been studied and optimized. The proposed sensor was successfully employed for BCT analysis by square wave voltammetry (SWV), and the attained linear dynamic range was (8.0 × 10−8 – 1.0 × 10−6 mol L−1), and the estimated limit of detection (LOD) and limit of quantitation (LOQ) were 1.799 × 10−8 mol L−1 and 5.453 × 10−8 mol L−1, respectively. The suggested electrochemical methodology was effectively utilized to determine BCT with satisfactory percentage recoveries in pharmaceutical preparation (99.69% ± 0.73) and human plasma samples. The developed approach underwent validation and was determined to be reproducible (RSD = 0.75%) and accurate (99.68% ± 0.76) following the ICH recommendations. The greenness of the established electrochemical protocol was assessed utilizing the Analytical Eco-Scale and Analytical GREEnness Metric Approach (AGREE).

Fast, Simple, and Sensitive Voltammetric Measurements of Acyclovir in Real Samples via Boron-Doped Diamond Electrode.

The voltammetric acyclovir (ACV) trace-level determination procedure has been introduced. This is the first time that a commercially available boron-doped diamond electrode (BDDE) coupled with differential-pulse voltammetry (DPV) has been used for this purpose. The commercially available BDDE is characterized by a short response time, low background current, and very good analytical parameters of ACV determination. Ultimately, DPV measurements using the BDDE in 0.075 mol L-1 PBS with a pH of 7.2 under optimized conditions achieved the lowest detection limit (LOD = 0.0299 nmol L-1) reported in the literature for voltammetric procedures. Moreover, it is highly resistant to the presence of various interfering agents and has been used to analyze pharmaceutical and municipal wastewater samples. The obtained results are consistent with measurements made using chromatographic reference methods.

Electrosynthesis of Highly Functionalized Quinolines through Radical Annulation-Polar Addition Cascade.

Synthesis of diversely functionalized quinoline-2-carboxylates is illustrated through electrochemical cross-dehydrogenative coupling between N-aryl glycinates and methylenecyclopropanes. An extensive range of distinct functionalities is well-compatible under these transition-metal- and oxidant-free mild electrochemical conditions, contributing to a broad substrate scope and practical applicability. Cyclic voltammetric measurements and control experiments suggested a formal [4 + 2] cycloaddition involving radical intermediates, followed by a cyclopropyl ring opening through nucleophilic polar addition, consecutively fabricating C-C and C-N bonds.

Fabrication of nanomolecular platform based immunosensor for non-invasive electrochemical detection of oral cancer: An in vitro study

Silver nanoparticles (AgNPs)-Chitosan (Chi) functionalized cysteine (cys)-SAM (self-assembled monolayer) based electrochemical, label free, ultrasensitive, non-invasive immunosensing nanomolecular platform has been fabricated for the detection of novel OC biomarker S-100. This has been achieved through bio-functionalization of AgNPs-Chi/cys/mini gold slides by covalent immobilization of anti-S100 antibodies. Cyclic voltammetric (CV) studies establish successful fabrication of anti-S100/AgNPs-Chi/Au nanomolecular platform. Differential pulse voltammetric (DPV) measurements reveal that anti-S100/Chi-AgNPs/Au is able to sense 50 fg mL-1 – 500 ng mL-1 of S100 in buffer and in spiked saliva samples within 120 s interaction time having improved favorable shelf life and specificity. The fabricated platform is very selective and able to detect S100 in OC patient/s saliva samples warrants realization of simple non-invasive electrochemical immunosensor for in situ or on-site applications (especially for remote areas) for early diagnosis of OC while offering bio-compatibility at low cost.

3D/2D-Bismuth Oxybromide Spheres with Selenium-Doped Graphitic Carbon Nitride Sheets: An Efficient Electrocatalyst for the Detection of Arsenic Drug Roxarsone.

Heavy metals are crucial carcinogenic agents threatening the environment and living habituates. Among them, arsenic (As) is an important metalloid that is categorized as a group I toxic carcinogen. Roxarsone (RX) is an organoarsenic antibiotic compound primarily used as a veterinarian drug and growth promoter for poultry animals. The extensive usage of RX increased the accumulation of As in living beings and the ecosystem. Therefore, we have prepared an electrochemical sensor based on 3D bismuth oxybromide with 2D selenium-doped graphitic carbon nitride (BOB/SCN) electrocatalyst for the rapid detection of RX. The elemental and structural details were thoroughly investigated with several spectroscopic techniques. The electrochemical properties were measured by impedance and voltammetric measurements. The electrocatalytic behavior toward the RX was estimated with different voltammetric methods. Therefore, our BOB/SCN-based electrochemical sensor demonstrated a low detection limit (2.3 nM), low quantification value (7.7 nM), optimal sensitivity (0.675 μA μM-1 cm-2), and good linear ranges (0.01-77 and 77-857 μM). Additionally, this sensor showed good electrochemical performance and was applied to monitor the RX in various real samples with remarkable recoveries. Based on these results, our BOB/SCN sensor is a promising electrochemical platform for determining RX.

Electrochemical Nitrogen Fixation at Phosphide Catalyst in Alkaline Medium: Electrocatalytic Approach Toward Validation and Determination of Ammonium Product

A catalytic system based on iron phosphide (Fe2P) has exhibited electrocatalytic activity toward N2-reduction reaction in alkaline medium (0.5 mol dm-3 NaOH). Based on voltammetric stripping-type electroanalytical measurements, Raman spectroscopic and spectrophotometric data, it can be stated that the Fe2P catalyst facilitates conversion of N2 to NH3, and the process is fairly selective with respect to the competing hydrogen evolution. A series of diagnostic electrocatalytic experiments (utilizing platinum nanoparticles and HKUST-1) have been proposed and performed to control purity of nitrogen gas and to probe presence of potential contaminants such as ammonia, nitrogen oxo-species and oxygen. On the whole, the results are consistent with the view that the interfacial reduced-iron (Fe0) centers, while existing within the network of P sites, induce activation and reduction of nitrogen, parallel to the water splitting (reduction) to hydrogen. It is apparent from Tafel plots and impedance measurements that mechanism and dynamics of nitrogen reduction depends on the applied electroreduction potential. The catalytic system exhibits certain tolerance with respect to the competitive hydrogen evolution and gives (during electrolysis at -0.4 V vs. RHE) the Faradaic efficiency, namely, the selectivity (molar) efficiency, toward production of NH3 on the level of 60%. Under such conditions, the NH3-yield rate has been found to be equal to 7.5 µmol cm-2 h-1 (21 µmol m-2 s-1). By referring to classic concepts of electrochemical kinetic analysis, the rate constant in heterogeneous units has been found to be on the moderate level of 1-2*10-4 cm s−1 (at -0.4 V). The above mentioned iron-phosphorous active sites, which are generated on surfaces of Fe2P particles, have also been demonstrated to exhibit strong catalytic properties during reductions of other electrochemically inert reactants, such as oxygen, nitrites and nitrates. Supplementary diagnostic experiments have also been carried out to control purity of nitrogen gas and to identify potential contaminants. To comment on general catalytic activity of Fe2P during electroreductions in alkaline medium, we have performed additional comparative measurements using such redox probes as O2, CO2, NO3 - and NO2 -.

A Dual-Channel Biosensor Enables Concurrent Detection of Pathogens and Antibiotic Resistance

Diarrhoeagenic infections, commonly treated with β-lactam antibiotics, contribute to antibiotic resistance - a pressing public health concern. Rapid monitoring of pathogen antibiotic resistance is vital to combat antimicrobial spread. Current bacterial diagnosis methods identify pathogens or determine antibiotic resistance separately, necessitating multiple assays. There is an urgent need for tools that simultaneously identify infectious agents and their antibiotic resistance at the point of care (POC). We developed an integrated electrochemical chip-based biosensor for detecting enteropathogenic E. coli. Leveraging an antibody against the virulence marker EspB, the dual-channel chip facilitated electrochemical impedance spectroscopy-based detection of EspB antigen (sensitivity of 10 ng/mL) and EspB-expressing bacteria. For β-lactam resistance profiling, a second channel enabled differential-pulse voltammetric measurement of hydrolyzed nitrocefin, a β-lactam analogue, demonstrating sensitive detection of the antibiotic resistance marker, β-lactamase at concentrations as low as 1 ng/mL. The integrated electrochemical biosensor successfully achieved simultaneous, rapid detection of double positive EspB- and β-lactamase-expressing bacteria, promoting advancements in POC clinical diagnosis.

Rational Design of Fluorophores Using MO Theory: Our Journey from BODIPYs to BOIMPYs

This short review demonstrates how MO-theoretical considerations can support the tailor-made design of new dye scaffolds, specifically the recently introduced BOIMPY class of fluorophores. Starting with historical and structural foundations, the influence of canonical streptocyanines on the electronic features of diarylmethenes and rhodamines is examined and the BODIPY scaffold is introduced as the primary structural inspiration for our work. The attachment of five-membered ring heterocycles at the meso position of the BODIPY core enables a relaxation into a co-planar and twofold chelating triarylmethene system. After introduction of two electron-withdrawing BF2 units, efficient rigidity is achieved since hindered rotation prevents non-radiative dissipation of energy via excited state relaxation. Hence, a lowered LUMO level allows the combination of a large red shift with high quantum efficiencies. The synthetic approach to BOIMPYs is straightforward and analogous to BODIPY syntheses starting from benzimidazole or tetrazole carbaldehydes. Cyclic voltammetric measurements prove that BOIMPYs are able to easily accept two electrons and might act as efficient photoredox catalysts.

First voltammetric analysis of two possible anticancer drug candidates using an unmodified glassy carbon electrode

Dimethyl 2-[2-(1-phenyl-4,5-dihydro-1H-imidazol-2-yl)hydrazinylidene]butanedioate (DIHB) and 8-(3-chlorophenyl)-2,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazine-3,4-dione (HDIT) are promising candidates for anticancer agents, the first analytical procedures of which are presented in this paper. The commercially available unmodified glassy carbon electrode (GCE) was used as a sensor for the individual and simultaneous differential pulse voltammetric (DPV) determination of these possible anticancer drugs. The findings concerning the electrochemical behaviour indicated that DIHB and HDIT display at GCE, as a sensor, the oxidation peaks at 1.18 and 0.98 V, respectively (vs. Ag/AgCl, 3.0 mol L−1 KCl) in the 0.125 mol L−1 acetate buffer of pH = 4.5, which were employed for their quantification. Various experimental parameters were carefully investigated, to achieve high sensitivity in voltammetric measurements. Finally, under the optimised conditions (t of 60 s, ΔEA of 75 mV, ν of 225 mV s−1, and tm of 2 ms), the proposed DPV procedure with the GCE demonstrated broad linear sensing ranges (1–200 nmol L−1—DIHB and 5–200 nmol L−1—HDIT), boasting the detection limits of 0.18 nmol L−1 for DIHB and 1.1 nmol L−1 for HDIT. Moreover, the developed procedure was distinguished by good selectivity, repeatability of DIHB and HDIT signals and sensor reproducibility. The practical application of this method was demonstrated by analysing the urine reference material without any prior treatment. The results showed that this environmentally friendly approach, with a modification-free sensor, is suitable for the sensitive, selective and rapid quantification of DIHB and HDIT.

SIMULTANEOUS DETERMINATION OF ASCORBIC ACID, URIC ACID, AND DOPAMINE ON CARBON NANOTUBE PASTE ELECTRODE

Background: Ascorbic acid (AA), uric acid (UA), and dopamine (DA) play crucial roles in human metabolism. These substances coexist in biological fluids, and their levels are directly associated with various pathologies. A significant problem encountered in the direct and simultaneous electrochemical detection of AA, UA, and DA is that these species present very close oxidation potentials on most electrode materials, leading to an overlap in the voltammetric response. Aim: The main goal of this work was to determine the concentration of AA, UA, and DA in a natural water sample on a carbon nanotube paste electrode (CNTPE). Methods: All voltammetric measurements were performed on a µAutolab potentiostat/galvanostat (Metrohm) connected to an electrochemical cell of three electrodes: working, reference (Ag/AgCl, KCl3.0M), and auxiliary (platinum). The working electrode was handmade in our laboratory. The following proportions were used to prepare the paste: 50% CNT + 50% mineral oil and 65% CNT + 35% mineral oil. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used for the electroanalytical study. Results: The linear ranges for the simultaneous determination of AA, DA, and UA by DPV were: 0.45 – 1.0 mM, 50 – 200 ?M, and 10 – 90 ?M, respectively. The LODs of the proposed method for AA, DA, and UA were: 7.97 mM; 8.57 ?M, and 5.96 ?M, respectively. The relative standard deviations (RSD) were 4.6, 2.8, and 1.6% for 0.45 mM of AA, 50 ?M of DA, and 50 ?M of UA. Discussion: The oxidation mechanism of: AA, UA, and DA is a process that involves two electrons and 2 protons. Electrochemical detection of DA in the presence of high levels of AA on carbon-based electrodes becomes difficult due to the catalytic oxidation of AA by DA. For the three molecules, AA, UA, and DA, it is observed that the oxidation peak currents increased with increasing concentration. Conclusions: CNTPE allowed the separation of the oxidation peaks of the ternary mixture of AA, UA, and DA by cyclic voltammetry and, when associated with DPV allowed the simultaneous quantitative determination of AA, UA, and DA.

Electrodeposited polyaniline modified CNT fiber as efficient counter electrode in flexible dye-sensitized solar cells

Carbon-based electrodes played a significant role toward the development of wearable and flexible photovoltaic energy devices in an efficient and affordable manners. Here, all-carbon-based electrodes composed of carbon nanotubes fiber (CNTF) have been used to fabricate a flexible wire shaped dye-sensitized solar cell (DSSC). A facile electrodeposited approach has been adopted to modify a CNTF with polyaniline (PANI) under acidic conditions. Both photoanode (TiO2@CNTs) and counter electrode (PANI@CNTs) twisted around each other, acted as electrons and hole collectors in the presence of redox couple (iodide/triiodide) as electrolyte. Scanning electron microscopy (SEM) images demonstrated the successful growth of TiO2 nanoparticles and conducting polyaniline (PANI) over the surface of CNTs fibers, as photoanode and counter electrode, respectively. Cyclic voltammetric (CV) measurements and electrochemical impedance spectroscopy (EIS), examined the reduction of triiodide and resistance of charge transfer. While the current-voltage measurements were carried out to check the performance of fabricated device when illuminated under simulated light source. With APNI modified counter electrode, device exhibited higher photoelectric conversion efficiency (3.57 %) under optimal conditions as compared to pristine CNTs fiber-based device with lower efficiency (2.26 %). The improved performance of modified counter electrode further confirmed by the lower peak separation (ΔEp= 0.42 V) and charge transfer resistance (RCE =19.28 Ω) in cyclic voltammetry and impedance spectroscopy, respectively. These fabricated electrodes could be promising alternate for metal-based electrodes in dye-sensitized solar cells due to its facile fabrication process, low cost, and higher chemical stability.

Electrochemical polymer synthesis using thiophene and pyrrole/carbazole: Their electrochemical behaviours and capacitor performance

In this study, carbazole-derived monomers were synthesized on ITO-coated PET via electrochemical reactions and conductivity measurements of the resulting polymeric films were performed by UV, FT-IR, NMR, TG-DTG, SEM and AFM analyses. Their spectroelectrochemical properties were investigated. The carbazole (C) based thiophene (Th) polymer abbreviated as pThC and its copolymer with pyrrole (Py), named as pThC-Py were obtained by electrochemical polymerization method. The surface stability of the resulting polymer films was good depending on time. The contact angle (CA) between the water and theco- polymer surface was determined by dropping 6.09 μL of pure water and CA average was calculated as 68.19° < 90°. According to the thermal analysis data of the polymers, the thermal stability of the pThC-Py was better than pThC as it had higher thermal decomposition temperature. Comparisons of electrical conductivity measurements of the polymer films were made depending on the temperature (25, 50 and 90 °C). Due to increasing temperature, the electrical conductivity of pThC-Py film was read as 29.3 S/cm at 90 °C, and also the electrical conductivity values of the pThC-Py were determined as 1.92 × 10−2 S/cm at 25 °C and 14.2 S/cm at 50 °C. Because of the high electrical conductivity of the pThC-Py, its capacitor performance was tried to be determined from cyclic voltammetric measurements. According to the voltammetric results, the power density (P) and the energy density (E) values of the synthesized substance were calculated as 290.532 W/g and 9.684 Wh/g, respectively. This indicates that the amount of energy the material storable is relatively high. Moreover, it is possible to say that it can be included in the classical capacitor class and in the supercapacitor category by improving its features. Moreover, since the electrical conductivity of pThC-Py is quite good, it is thought that it may be suitable for use in electronic devices.

Electrochemical Oxidation of Ranitidine using a Boron-Doped Diamond Electrode in the Presence of Anionic Surfactant: A Comprehensive Investigation

Ranitidine (RAN) is a drug from the histamine H2 receptor antagonist class and is used to prevent excessive production of stomach acid. An electrochemical investigation of the RAN in pharmaceutical preparation and spiked human urine was performed for the using a boron-doped diamond electrode (BDDE). Voltammetric measurements were performed in a pH 11 BR solution supplemented with the anionic surfactant, sodium dodecyl sulfate (SDS). In the proposed method using optimized experimental conditions, linearity was obtained for RAN in the concentration range of 0.8-50.0 μM. The LOD value obtained is 0.22 μM. Good selectivity, accuracy, precision, and acceptable repeatability were also achieved in this proposed electrochemical sensor. Finally, this electrochemical sensor was successfully used for RAN detection in pharmaceutical samples.

Construction of 3D spinel binary metal oxide flower decorated 1D halloysite nanotube electrocatalyst for the selective detection of arsenic drug pollutant roxarsone

Heavy metals, including arsenic (As), are categorized as a Group I toxic carcinogen and pose significant threats to the environment and habitats. Roxarsone (RXN) is an organoarsenic antibiotic drug commonly employed as a veterinary curative agent and growth promoter for poultry. Due to its widespread use, it substantially contributes to the accumulation of As in humans and ecosystems. Therefore, it is essential to monitor this potential drug in various real-world samples with high accuracy. Consequently, we have designed 3D zinc cobalt oxide (ZCO) with a 1D halloysite nanotube (HNT) based electrochemical sensor. The functional and morphological features of the electrocatalysts were evaluated with numerous analytic methods. The electrocatalytic property was investigated with different voltammetric measurements. Based on the outcomes, our ZCO/HNT-modified sensor displayed good linear ranges (0.01 to 127 μM and 127 μM to 1147 μM), low detection (1.6 nM), and quantification (5.2 nM) limits, optimal sensitivity (0.465 μA μM−1 cm−2), good selectivity, remarkable performance, and good stability results. Further, this sensor was applied to monitor RXN in various real-world samples and consequently, obtained the well-resolved results. Hence, our ZCO/HNT is an efficacious electrocatalyst for the precise detection of RXN.

Effect of Temperature on the Removal of Interferences in the Voltammetric Procedure for the Determination of Cr(VI).

The aim of this paper was to investigate the effect of temperature on the removal efficiency of surfactant-induced interferences. Surfactants were removed as a result of mixing with XAD-7 resin. The study was carried out using the example of Cr(VI) determination by adsorption stripping voltammetry (AdSV). Measurements were carried out using a solution containing Cr(VI), acetate buffer (pH = 6.2), DTPA, KNO3, and different surfactants. Ten mL of the solution was mixed with 0.5 g of XAD-7 resin at different temperatures for 5 min prior to voltammetric measurement. The effect of the mixing temperature of the sample with the resin on the voltammetric Cr(VI) signal in the presence of different surfactants was studied in the range from 20 to 60 °C. The proposed method of removing interference from surfactants by mixing the sample with the XAD-7 resin at 60 °C was used for the determination of trace amounts of Cr(VI) in river water containing non-ionic, anionic, cationic surfactants, and biosurfactants.

Post-macrocyclization strategy to octaphenoxy-substituted zinc pyrazinoporphyrazine, its photochemical and electrochemical properties

An efficient post-macrocyclization strategy to new octaphenoxy-substituted zinc pyrazinoporphyrazine has been developed. This approach allows avoiding the template synthesis of the target compound from the phenoxy-substituted dinitrile, during which oligomerization and phenol release occur. The possibility of obtaining the initial octachloropyrazinoporphyrazine using template synthesis activated thermally and using microwave irradiation has been shown. Octaphenoxy-substituted zinc pyrazinoporphyrazine demonstrates short but intense triplet signals in triplet absorption spectrum and substantial singlet oxygen quantum yield (ΦΔ = 0.34). The fluorescent properties and fluorescence decay kinetics of target porphyrazines were studied. In contrast to the initial poorly soluble chlorinated complex, cyclic voltammetric measurements show both reduction and oxidation processes. Two waves of reduction and one wave of oxidation were observed. The electron-donating nature of phenoxy groups compared to chlorine groups is shown.