A Facile Electrochemical Sensor Labeled by Ferrocenoyl Cysteine Conjugate for the Detection of Nitrite in Pickle Juice

Diazo-functionalised immunoelectrochemical sensor for the detection of ochratoxin a in foods

Ochratoxin A (OTA) is a toxic fungal metabolite that is commonly found in cereals and animal feed. It is economically damaging and potentially hazardous to human health. Herein, we propose an electrochemical immunosensor for the rapid detection of OTA using anti-OTA antibodies and diazonium-functionalized, screen-printed electrodes. We attached 4-aminobenzoic acid to an electrode surface, activated the carboxyl groups on the surface with carbodiimide, and attached an antibody to the diazo layer. Subsequently, we used bovine serum protein as a blocker to prevent non-specific antigens from binding to the antibody. We evaluated the performance of the sensor by cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry. The sensor is highly specific and sensitive, has good linear responses in the range 20-200 ng/mL, a limit of detection of 0.5 ng/mL, and good recoveries of 90.5%-100.9% in spiked samples. It can be stored at 4 °C for approximately 2 weeks, and is highly stable, with a current response variation of no more than 4.6%.

Contemporary Developments in Ferrocene Chemistry: Physical, Chemical, Biological and Industrial Aspects

Ferrocenyl-based compounds have many applications in diverse scientific disciplines, including in polymer chemistry as redox dynamic polymers and dendrimers, in materials science as bioreceptors, and in pharmacology, biochemistry, electrochemistry, and nonlinear optics. Considering the horizon of ferrocene chemistry, we attempted to condense the neoteric advancements in the synthesis and applications of ferrocene derivatives reported in the literature from 2016 to date. This paper presents data on the progression of the synthesis of diverse classes of organic compounds having ferrocene scaffolds and recent developments in applications of ferrocene-based organometallic compounds, with a special focus on their biological, medicinal, bio-sensing, chemosensing, asymmetric catalysis, material, and industrial applications.

Enzyme-free glucose sensors with efficient synergistic electro-catalysis based on a ferrocene derivative and two metal nanoparticles

Gold electrodes (GE) were modified by the deposition of copper nanoparticles (CuNPs) and cobalt nanoparticles (CoNPs), followed by drop-casting of the ferrocene derivative FcCO-Glu-Cys-Gly-OH (Fc-ECG), resulting in two enzyme-free electrochemical sensors Fc-ECG/CuNPs/GE and Fc-ECG/CuNPs/GE. The ferrocene-peptide conjugate acts as an effective redox mediator for glucose oxidation, while metal nanoparticles acted as non-biological sites for glucose oxidation. Field emission scanning electron microscopy (FESEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out for characterization, while differential pulse voltammetry (DPV) was used for glucose quantification. Under optimized conditions, DPV shows a linear relationship between glucose concentration and the peak current. Both sensors showed a surprisingly high sensitivity of 217.27 and 378.70 μA mM⁻¹ cm⁻², respectively. A comparison to other glucose sensors shows a sensitivity that is 25 times higher. The sensors exhibit good reproducibility, stability, and repeatability. In injection experiments, recovery rates were 87.39–107.65% and 100.00–106.88%, respectively.

We exploit the ferrocene–glutathione conjugate Fc-ECG as electron transfer mediator and make use of gold electrodes that were modified with either copper or cobalt nanoparticles to give sensor surfaces that exhibit excellent catalytic activity of glucose oxidation.

Sensing and sensitive visualization of latent fingerprints on various surfaces using a versatile fluorescent aggregation-induced emission-based coumarin derivative

The marked rise in criminal activity in society has made a difficult task for forensic scientists who aim to track any crime scene effectively, therefore visualization of latent fingerprints (LFPs) plays an increasingly vital role in forensics. In the present report, a highly sensitive solvatochromism, aggregation-induced emission-based 2-(4-nitrophenyl)-3H-benzocoumarin fluorescent dye (CFD) was fabricated using an ultrasonication protocol. The fluorescence properties of the CFD were analyzed using fluorescence spectrophotometer. The CFD produced a greenish yellow emission in solid and fluid states. An in-depth visualization of LFPs showed detailed ridge patterns under normal and ultraviolet light sources (254 and 365 nm) due to the excellent chemisorption of CFD onto the ridge patterns on the finger. All three types of ridge details were visualized without any background interference when using a simple and quick powder dusting method. Results revealed that, the present fluorescent dye can be used successfully for detection of latent fingerprints (LFPs) on various nonporous substrates surfaces, in organic light-emitting diodes applications (OLEDs), and for electrochemical sensing.

The construction of a simple sensor for the simultaneous detection of nitrite and thiosulfate by heme catalysis

Several simple sensors were fabricated through a one-step method. By depositing electro-active compounds, such as β-cyclodextrins (β-CD), heme, dopamine (DA), or Fc-ECG, onto a screen-printed electrode (SPE), the successful simultaneous detection of nitrite (NO2 -) and thiosulfate (S2O3 2-) ions was observed. Under optimal operating conditions, the notable electrocatalytic abilities of a Heme/SPE sensor were detected for the oxidation of NO2 - and S2O3 2-, with remarkable peak potential differences, after characterization via SEM, CV, and DPV. Linear relationships were obtained in the ranges of 5.0-200.0 μmol L-1 and 1.0-100.0 μmol L-1 for the current response versus concentration of NO2 - and S2O3 2-, respectively. The limits of detection were determined to be 1.67 and 0.33 μmol L-1 while the sensitivities of detection were noted to be 0.43 and 1.43 μA μM-1 cm-2, respectively. During the detection of NO2 - and S2O3 2-, no interfering common ions were observed. Furthermore, average recoveries from 96.0 to 104.3% and a total R.S.D. of less than 3.1% were found for the detection of NO2 - and S2O3 2- in pickled juice and tap water using the simple sensor. These results showed that rapid and precise measurements for actual application in NO2 - and S2O3 2- detection could be conducted in food samples, indicating a potential use in food safety.

The Use of Factorial Design and Simplex Optimization to Improve Analytical Performance of In Situ Film Electrodes

This work presents a systematic approach to determining the significance of the individual factors affecting the analytical performance of in-situ film electrode (FE) for the determination of Zn(II), Cd(II), and Pb(II). Analytical parameters were considered simultaneously, where the lowest limit of quantification, the widest linear concentration range, and the highest sensitivity, accuracy, and precision of the method evidenced a better analytical method. Significance was evaluated by means of a fractional factorial (experimental) design using five factors, i.e., the mass concentrations of Bi(III), Sn(II), and Sb(III), to design the in situ FE, the accumulation potential, and the accumulation time. Next, a simplex optimization procedure was employed to determine the optimum conditions for these factors. Such optimization of the in situ FE showed significant improvement in analytical performance compared to the in situ FEs in the initial experiments and compared to pure in situ FEs (bismuth-film, tin-film, and antimony-film electrodes). Moreover, using the optimized in situ FE electrode, a possible interference effect was checked for different species and the applicability of the electrode was demonstrated for a real tap water sample.

Application of Microfluidic Chip Technology in Food Safety Sensing

Food safety analysis is an important procedure to control food contamination and supervision. It is urgently needed to construct effective methods for on-site, fast, accurate and popular food safety sensing. Among them, microfluidic chip technology exhibits distinguish advantages in detection, including less sample consumption, fast detection, simple operation, multi-functional integration, small size, multiplex detection and portability. In this review, we introduce the classification, material, processing and application of the microfluidic chip in food safety sensing, in order to provide a good guide for food safety monitoring.

Solvent stir bar microextraction technique with three-hollow fiber configuration for trace determination of nitrite in river water samples

In this work, trace determination of nitrite in river water samples was studied using solvent stir bar microextraction system with three-hollow fiber configuration (3HF-SSBME) as a preconcentration step prior to UV-Vis spectrophotometry. The obtained results showed that the increase in the number of solvent bars can improve the extraction performance by increasing the contact area between acceptor and sample solutions. The extraction process relies on the well-known oxidation-reduction reaction of nitrite with iodide excess in acidic donor phase to form triiodide, and then its extraction into organic acceptor phase using a cationic surfactant. Various extraction parameters affecting the method were optimized and examined in detail. Detection limit of 1.6 μg L^-1 and preconcentration factor of 282 can be attained after an extraction time of 8 min under the optimum conditions of this technique. The proposed method showed a linear response up to 1000 μg L^-1 (r² = 0.996) with relative standard deviation values less than 4.0%. The accuracy of the developed method was assessed using the Griess technique. Finally, the proposed method was successfully employed for quantification of nitrite in river water samples (Ghezelozan, Zanjan, Iran).