Dealing with interference challenge in the electrochemical detection of As(III) —A complexometric masking approach

Copper ion has been reported to be a major interference in the electrochemical detection of arsenic (III) ion in water. Therefore the development of a simple approach to alleviate this interference challenge is important. We present the use of ammonia solution as a masking agent for Cu(II) interference in the square wave anodic stripping voltammetry of As(III) on a gold nanoparticle modified glassy carbon electrode (GCE). AuNPs were electrochemically deposited by cyclic voltammetry on a GCE from a potential range of − 400 mV to 1100 mV for 10 cycles. Square wave anodic stripping voltammetry (SWASV) was used to detect As(III) in water with and without Cu(II) based on the following optimised conditions: pH = 3, deposition potential = − 600 mV, and deposition time = 60 s. Ammonia solution was added to the analyte solution and the effect on mitigating copper interference was studied. The presence of ammonia complexed the Cu(II) ion thereby excluding Cu(II) from interfering with the As(III) signal.     

CuS–MWCNT based electrochemical sensor for sensitive detection of bisphenol A

The rapid and simple detection of bisphenol A is very important for the safety and reproduction of organisms. Here, a sensitive and reliable electrochemical sensor was established for bisphenol A detection based on the high amplification effect of copper sulfide-multi-walled carbon nanotube (CuS–MWCNT) nanocomposites. The flower-like CuS–MWCNT were successfully synthesized by a simple hydrothermal method accompanied by polyvinylpyrrolidone (PVP). Compared with bare glassy carbon electrode (GCE), CuS–MWCNT modified GCE could amplify the electrochemical signals in about ten times, which was attributed to the synergistic effect of CuS and MWCNT. The MWCNT could increase the specific surface area of electrodes and improve the electrode activity. The integration of CuS could further enhance the electrode conductivity as well as accelerate the electron transfer rate. Raman spectra and transmission electron microscope (TEM) were used to characterize the successful fabrication of CuS–MWCNT nanocomposites and its uniform and monodispersed morphology. Under optimizing conditions, the oxidation currents of bisphenol A via the differential pulse voltammetric (DPV) showed a good linear relationship with its concentration in a wide range of 0.5–100 μM, with a detection limit of 50 nM. This electrochemical sensor of bisphenol A provided a convenient and economical platform with high sensitivity and reproducibility, which had great potential in environmental monitoring.     

Cerium oxide nanofiber–based electrochemical immunosensor for detection of sepsis in biological fluid

Sepsis causes life-threatening complications with the highest burden of death and medical expenses in hospitals worldwide. Despite the progression of targeted therapies for sepsis, the challenge of early diagnosis of sepsis-related biomarkers remains. The analysis of the TNF-α and sTREM-1 in biological fluids provides essential information for effective treatments. In this work, we report developing an electrochemical immunosensor for the rapid detection of TNF-α and sTREM-1 proteins in human plasma samples. First, using the electrospinning process, cerium oxide nanofibers were synthesized. Subsequently, the antibodies corresponding to the targeted proteins are immobilized onto the surface-functionalized working electrodes using NHS/EDC chemistry. The proposed immunosensor’s performance in a biological fluid was assessed using an analytical electrochemistry approach. The limit of detection for the electrochemical immunosensors was 0.51 and 0.41 pg/mL for TNF-α and sTREM-1, respectively, with high selectivity and sensitivity for the use as a point of care device.

     

Sensitive determination of 17β-estradiol in river water using a graphene based electrochemical sensor

In this study, a novel material for the electrochemical determination of 17β-estradiol using an electrode based on reduced graphene oxide and a metal complex porphyrin has been applied to environmental monitoring. The electrochemical profile of the proposed electrode was analyzed by differential pulse voltammetry, which showed a shift of the oxidation peak potential of 17β-estradiol to 150 mV in a less positive direction compared to the bare reduced graphene oxide electrode. DPV experiments were performed in PBS at pH 7.0 to determine 17β-estradiol without any previous step of extraction, cleanup, or derivatization, in the range of 0.1–1.0 μmol L⁻¹ with a detection limit archived at 5.3 nmol L⁻¹ (1.4 μg L⁻¹). The proposed sensor was successfully applied in the determination of 17β-estradiol in a river water sample without any purification step and was successfully analyzed under the standard addition method. All the obtained results were in agreement with those from the HPLC procedure.     

Double molecular imprinting – a new sensor concept for improving selectivity in the detection of polycyclic aromatic hydrocarbons (PAHs) in water

It is now well recognised that the quality control (QC) of all types of analyses, including environmental analyses depends on the appropriate use of reference materials. One of the ways to check the accuracy of methods is based on the use of Certified Reference Materials (CRMs), whereas other types of (not certified) Reference Materials (RMs) are used for routine quality control (establishment of control charts) and interlaboratory testing (e.g. proficiency testing). The perception of these materials, in particular with respect to their production and use, differs widely according to various perspectives (e.g. RM producers, routine laboratories, researchers). This review discusses some critical aspects of RM use and production for the QC of environmental analyses and describes the new approach followed by the Measurements & Testing Generic Activity (European Commission) to tackle new research and production needs.     

Synthesis of new bis-benzylidene-hydrazides as a sensitive chromogenic sensor for naked-eye detection of CN¯ and AcO¯ ions

Some new bis-benzylidene-hydrazides were synthesized via a condensation reaction of the corresponding azo dyes with adipic acid dihydrazide. All compounds because of the three possible stereoisomers showed four sets of signals in NMR. The anion recognition studies exhibited that the nitro bis-benzylidene-hydrazide derivative acts as a highly sensitive and selective chromogenic sensor for naked-eye detection of CN¯ and AcO¯ ions, with a distinct color change from yellow to blue and yellow to purple, respectively. The limit of detection (LOD) was found for 1d toward CN¯ to be 1.1?μM. The result of the Job's plot indicated stoichiometry of binding between chemosensor and anions is found to be 1:2.     

Ionic liquid–graphene hybrid nanosheets-based electrochemical sensor for sensitive detection of methyl parathion

In this work, ionic liquid–graphene nanosheets (IL–GNs) were synthesised and used as an enhanced material for sensitive detection of methyl parathion (MP) by electrochemical method. IL–GNs were characterised by UV–Vis spectroscopy, transmission electron microscopy (TEM), X-ray photo-electron spectroscopy (XPS), Fourier transform Infrared (FT-IR) spectroscopy and Raman spectroscopy, which confirmed that IL was successfully covered on the surface of GNs. Significantly, due to the coupling of excellent properties of GNs and IL, the IL–GNs-modified glassy carbon electrode (IL–GNs/GCE) showed higher signals for MP response than the GNs/GCE and bare GCE. At the IL–GNs/GCE, the peak currents increase linearly with the concentration of MP in the range of 5.3 ng/mL to 2.6 μg/mL with the detection limit of 1.1 ng/mL, which was better than other enzyme-based and enzymeless sensors. The IL–GNs-based electrochemical sensor was also successfully demonstrated for the detection of water sample with satisfactory results. Furthermore, the proposed electrochemical sensor exhibited satisfied stability and reproducibility. The simple sensing platform can be extended to detect other organophosphate pesticide.     

Gold nanoparticle-based colorimetric sensor for studying the interactions of β-amyloid peptide with metallic ions

In this paper, a kind of β-amyloid peptide (Aβ1-16) conjugated gold nanoparticles (Aβ1-16@GNPs) are prepared and employed as colorimetric indicator for studying the interaction of β-amyloid peptide with metallic ions (e.g. Zn²⁺ and Ca²⁺). In the presence of Zn²⁺, mono-dispersing Aβ1-16@GNPs enable to form aggregates or attach on the SHG-44 (human glioma cell) cellular surface which results in significant color change of the solution. The experimental results indicate that Zn²⁺ can interact with Aβ1-16 and form Zn²⁺-β-amyloid peptide complexes. In particular, in the presence of Zn²⁺, a time-dependent interaction of cells with Aβ1-16@GNPs has been observed that may suggest different expression levels of β-amyloid peptide related proteins in various cell cycles. In addition, the aggregating/binding process can be easily reversed by adding EDTA, a good chelated ligand of Zn²⁺, which gives further proof of the interaction mechanism.     

A novel hierarchical nanobiocomposite of graphene oxide–magnetic chitosan grafted with mercapto as a solid phase extraction sorbent for the determination of mercury ions in environmental water samples

New mercapto-grafted graphene oxide–magnetic chitosan (GO–MC) has been developed as a novel biosorbent for the preconcentration and extraction of mercury ion from water samples. A facile and ecofriendly synthesis procedure was also developed for modification of GO–MC with 3-mercaptopropyltrimethoxysilane. The prepared nanocomposite material (mercapto/GO–MC) was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and energy-dispersive X-ray spectroscopy (EDX). The mercury analysis was performed by continuous-flow cold vapor atomic absorption spectrometry. The parameters affecting the extraction and preconcentration processes were carried out. The optimum conditions were found to be 60 mg of sorbent, pH of 6.5, 10 min for adsorption time, 3 mL of HCl (0.1 mol L⁻¹)/thiourea (2% w/v) as the eluent and 250 mL for breakthrough volume. An excellent linearity was achieved in the range of 0.12–80 ng mL⁻¹ (R² = 0.999) at a preconcentration factor of 80. The limit of detection and quantification were achieved as 0.06 ng mL⁻¹ and 0.12 ng mL⁻¹, respectively. A good repeatability was obtained with the relative standard deviation (RSD) of 4.7%. Furthermore, real water samples were analyzed and good recoveries were obtained from 95 to 100%.     

Carbon-dot-based dual-emission nanohybrid produces a ratiometric fluorescent sensor for in vivo imaging of cellular copper ions

A sensitive biosensor: A strategy for the intracellular imaging of Cu(2+) ions has been developed by integrating a recognition molecule, N-(2-aminoethyl)-N,N,N'tris(pyridin-2-ylmethyl)ethane-1,2-diamine (AE-TPEA), into a hybrid system composed of carbon and CdSe/ZnS quantum dots.     

Platinum electrode coated with a bentonite–carbon composite as an environmental sensor for detection of lead

A Pt wire coated with a bentonite–carbon composite in a poly(vinyl chloride) membrane was used for detection of lead. The sensor has a Nernstian slope of 29.42±0.50 mV per decade over a wide range of concentration, 1.0×10⁻⁷ to 1.0×10⁻³ mol L⁻¹ Pb(NO₃)₂. The detection limit is 5.0×10⁻⁸ mol L⁻¹ Pb(NO₃)₂ and the electrode is applicable in the pH range 3.0–6.7. It has a response time of approximately 10 s and can be used at least for three months. The electrode has good selectivity relative to nineteen other metal ions. The practical analytical utility of the electrode is demonstrated by measurement of Pb(II) in industrial waste and river water samples.     

The role of low levels of water in the electrochemical oxidation of α-tocopherol (vitamin E) and other phenols in acetonitrile

The phenol, α-tocopherol, can be electrochemically oxidised in a -2e(-)/-H(+) process to form a diamagnetic cation that is long-lived in dry organic solvents such as acetonitrile and dichloromethane, but in the presence of water quickly reacts to form a hemiketal. Variable scan rate cyclic voltammetry experiments in acetonitrile with carefully controlled amounts of water between 0.010 M-0.6 M were performed in order to determine the rate of reaction of the diamagnetic cation with water. The water content of the solvent was accurately determined by Karl Fischer coulometric titrations and the voltammetric data were modelled using digital simulation techniques. The oxidation peak potential of α-tocopherol measured during cyclic voltammetry experiments was found to shift to less positive potentials as increasing amounts of water (0.01-0.6 M) were added to the acetonitrile, which was interpreted based on hydrogen-bonding interactions between the phenolic hydrogen atom and water. Several other phenols were examined and they displayed similar voltammetric features to α-tocopherol, suggesting that interactions of phenols with trace amounts of water were a common occurrence in acetonitrile. The H-bonding interactions of α-tocopherol with water were also examined via NMR and UV-vis spectroscopies, with the voltammetric and spectroscopic studies extended to include other coordinating solvents (dimethyl sulfoxide and pyridine).     

Supramolecular assembly of a new squaraine and β-cyclodextrin for detection of thiol-containing amino acids in water

A new unsymmetrical aniline-based squaraine (SQ2) bearing binding unit of Hg²⁺ ion was designed and synthesised. SQ2 can form 1:2 inclusion complex with β-cyclodextrin, and the resulting complex, which undergoes absorption and fluorescence bleaching upon binding Hg²⁺, can serve as a turn-on colorimetric or fluorescent chemosensor in organic solvent-free aqueous solution for thiol-containing amino acids with high selectivity and tunable measuring range.     

Recirculation—a novel approach to quantify interstitial analytes in living tissue by combining a sensor with open-flow microperfusion

We report a novel approach to quantify interstitial analytes in living tissue by combining open-flow microperfusion (OFM) with a sensor and the re-circulation method. OFM is based on the unrestricted exchange of molecules between the interstitial fluid (ISF) and a perfusion medium through macroscopic perforations that enables direct access to the ISF. By re-circulating the perfusate and monitoring the changes of the analytes’ concentration with a sensor, the absolute analyte concentration in the ISF can be calculated. In order to validate the new concept, the absolute electrical conductivity of the ISF was identified in six subjects to be 1.33?±?0.08 S/m (coefficient of variation CV?=?6 %), showing the robustness of this approach. The most striking feature of this procedure is the possibility to monitor several compounds simultaneously by applying different sensors which will allow not only the determination of the concentration of a single substance in vivo but also the simultaneous dynamics of different analytes. This will open new fields in analytical chemistry, pharmacology, as well as clinical experimental research.     

Recent developments in the use of metal oxides for photocatalytic degradation of pharmaceutical pollutants in water—a review

In recent years, metal oxide semiconductors have been explored as photocatalysts for the degradation of organic contaminants in water/wastewater. The uniqueness of these oxide materials is in their ability to harness energy in the UV/Vis range, their relative ease of synthesis, low cost, and their general high surface ratio to mass, etc. Thus, these materials have consequently drawn much profound interest in environment applications, particularly pharmaceutical drugs for photocatalytic degradation. Furthermore, the non-toxic nature of most metal oxide semiconductors means they are convenient for water treatment works, resulting in safe drinking water for humans and safe environments for aquatic mammals. Pharmaceuticals are emerging pollutants that are increasingly being found in water systems. They have been detrimental to the human and animal health. In this article, pharmaceutical drugs abatement from water via photocatalysis process using oxide-based advanced metals such as TiO₂, ZnO, Fe₂O₃,WO₃, and Bi₂WO₆ is discussed. Degradation of various drugs at laboratory scale have been assessed and examples cited. Various approaches to metal oxides modifications and synthesis methods to improve degradation efficiency have also been discussed. Effects of experimental/operational parameters in the degradation process have been compiled and compared. Finally, a short preview of degradation of pharmaceuticals pilot scales is also highlighted.     

Construction of ceo2/rgo/gce electrochemical sensor for the determination of histamine in fishEI北大核心CSCD

By preparing nano-CeO2 (CeO2) and reduced graphene oxide (RGO), an electrochemical sensor based on CeO2/RGO composite was constructed for the detection of histamine. The morphology and structure of the composites were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical behavior of histamine on the sensor was studied by cyclic voltammetry (CV), and the conditions such as the type proportion and addition amount of the composite scanning rate and buffer pH were optimized. The results showed that the optimal conditions were as follows: The mass ratio was m(CeO2): M(RGO)=1: 0.25, the addition amount of composite material was 10 μL, the scanning rate was 300 mV/s and the pH of buffer solution was 8. A good linear relationship was observed between the peak current and the concentration of histamine in the range of 0.25–100 mg/L with the detection limit of 0.16 mg/L. The CeO2/RGO/GCE electrochemical sensor has been applied to the determination of histamine in fish samples with the spiked recoveries of 98.4% −104%. The method can be used to determine histamine content in fish products. © 2023, Youke Publishing Co.,Ltd. All rights reserved.