The potential of electrochemistry for one-pot and sensitive analysis of patent blue V, tartrazine, acid violet 7 and ponceau 4R in foodstuffs using IL/Cu-BTC MOF modified sensor

Recent advances in electrochemical detection of common azo dyes

PURPOSE

Food forensics is an emerging field and the initial part of this review showcases the toxic effects and the instrumental methods applied for the detection of the most commonly used azo dyes. Electrochemical detection has a lot of advantages and hence the significance of the most important techniques used in the electrochemical detection is discussed. The major part of this review highlights the surface modified electrodes, utilized for the detection of the most important azo dyes to achieve low detection limit (LOD).

METHODS

A thorough literature study was conducted using scopus, science direct and other scientific databases using specific keywords such as toxic azo dyes, electrochemical detection, modified electrodes, LOD etc. The recent references in this field have been included.

RESULTS

From the published literature, it is observed that with the growing interests in the field of electrochemical techniques, a lot of importance have been given in the area of modifying the working electrodes. The results unambiguously show that the modified electrodes outperform bare electrodes and offer a lower LOD value.

CONCLUSION

According to the literature reports it can be concluded that, compared to other detection methods, electrochemical techniques are much dependable and reproducible. The fabrication of the electrode material with the appropriate modifications is the main factor that influences the sensitivity. Electrochemical sensors can be designed to be more sensitive, more reliable, and less expensive. These sensors can be effectively used by toxicologists to detect trace amounts of harmful dyes in food samples.

An update on the sample preparation and analytical methods for synthetic food colorants in food products

Colorants, especially synthetic colorants, play a crucial role in enhancing the aesthetic qualities of food owing to their cost-effectiveness and stability against environmental factors. Ensuring the safe and regulated use of colorants is essential for maintaining consumer trust in food safety. Various preparation and analytical technologies, which are continuously undergoing improvement, are currently used to quantify of synthetic colorants in food products. This paper reviews recent developments in analytical techniques for synthetic food colorants, detection and compares the operational principles, advantages, and disadvantages of each technology. Additionally, it also explores advancements in these technologies, discussing several invaluable tools of analysis, such as high-performance liquid chromatography, liquid chromatography-tandem mass spectrometry, electrochemical sensors, digital image analysis, near-infrared spectroscopy, and surface-enhanced Raman spectroscopy. This comprehensive overview aims to provide valuable insights into current progress and research in the field of food colorant analysis.

Composition Design of Ni-Nano-Cu-BTC@Ag Coatings with Low Friction and Their Intelligent Electrical Control Behavior

At present, Ni-based coatings are rarely used in the field of voltage control friction because of their poor antifriction, wear resistance, and conductive properties. Therefore, in this paper, Cu-BTC@Ag nanocrystals were used to enhance the nickel coatings, and the effect of voltage on their tribological properties was also investigated. It was found that the grains of coating were refined via the addition of Cu-BTC@Ag nanocrystals, leading to an improvement in the hardness and corrosion resistance of this composite coating. The tribological performance of nickel composite coating could be controlled under different electrical fields. With the comparison of the pure Ni-based coating, the average friction coefficient and wear volume of its composite coating with 5 wt % Cu-BTC@Ag were reduced by 7.0 and 91.8%, respectively, which showed excellent wear resistance without an applied voltage. Under the condition of 20 V, the 5 wt % Cu-BTC@Ag/Ni-based composite coating owned outstanding antifriction performance. Therefore, Cu-BTC@Ag played an intelligent role in regulating the friction of Ni-based coatings under an external voltage. It is due to the accumulation of Cu-BTC@Ag nanocrystals on the surface of the coating under the action of voltage, which played the role of supporting load and effectively reducing wear.

Individual and Simultaneous Electrochemical Detection of Allura Red and Acid Blue 9 in Food Samples Using a Novel La2YCrO6 Double Perovskite Decorated on HLNTs as an Electrocatalyst

The present study involved the synthesis of La2YCrO6 double perovskites using a sol-gel approach. Additionally, a sonication method was implemented to prepare La2YCrO6 double perovskites decorated on halloysites (La2YCrO6/HLNTs). The La2YCrO6/HLNTs exhibited remarkable conductivity, electrocatalytic activity, and rapid electron transfer. It is imperative to possess these characteristics when overseeing the concurrent identification of Allura red (AR) and acid blue 9 (AB) in food samples. The development of the La2YCrO6/HLNTs was verified through the utilization of diverse approaches for structural and morphological characterization. The electrochemical techniques were employed to evaluate the analytical techniques of La2YCrO6/HLNTs. Impressively, the La2YCrO6/HLNTs demonstrated exceptional sensitivity, yielding the lowest detection limit for AR at 8.99 nM and AB at 5.14 nM. Additionally, the linear concentration range was 10-120 nM (AR and AB). The sensor that was developed exhibited remarkable selectivity, and the feasibility of AR and AB in the food sample was effectively monitored, resulting in satisfactory recoveries.

Fluorescent composite based on peptide nanotubes activating coumarin 6 for sensitive detection of new coccine in food samples

New coccine (NC), as a kind of common colorant, has been frequently used in our daily life. Herein, the fluorescent composite (PNTs@C6) prepared by the hydrophobic non-covalent interaction between peptide nanotubes and coumarin 6 (C6) was designed for the determination of NC. Due to the activation of C6 by peptide nanotubes, the composite exhibits strong green fluorescence emission, which can be selectively quenched by NC through the inner filter effect. Therefore, a new fluorescent method based on the PNTs@C6 composite for NC detection was constructed. Under optimal conditions, the fluorescence quenching of the sensor exhibits a good linear relationship with the concentration of NC in the range of 0.01-10 μM and the limit of detection is 3.6 nM. Furthermore, the strategy shows simplicity, rapid response and high selectivity and has been successfully applied to the detection of NC in food samples.

Magnetic ZnFe2O4 composite advances SERS assay for Patent blue V

BACKGROUND

Patent blue V (PbV) an Azo colorant because of its high toxicity to children has been severely limited in food industry. However, frequently the abuse of PbV in some artificial foods is still exposed by media. Current methods for the detection of PbV have to perform tedious pre-processing and the detection sensitivity and speed are required to be further improved.

RESULTS

In this work, we immobilize gold nanoparticles (Au NPs) on the surface of ZnFe2O4 with aid of Inositol hexaphosphate (IP6) to prepare a novel magnetic surface-enhanced Raman scattering (SERS) substrate (designated as ZnFe2O4-IP6-Au NPs) for rapid detection of PbV in beverages. Synergistic effect of magnetic enrichment, magnetic inducing improvement effect (MIIE) and efficient charge transfer (CT) enables ZnFe2O4-IP6-Au NPs-based SERS assay to achieve limit of detection of PbV down to 1.31 × 10-8 mol/L and a concentration linear relationship ranging from 8.6 × 10-4 to 8.6 × 10-8 mol/L. The detection recoveries for PbV in beverages locate in the range from 98.1 to 102.5 %, meaning the feasibility of method. In addition, the presence of IP6 protection greatly improves the storage stability of ZnFe2O4-IP6-Au NPs.

SIGNIFICANCE

ZnFe2O4-IP6-Au NPs substrates with excellent SERS performance could on-site, rapidly and sensitively detect PbV. As a perspective, magnetic-composite-based SERS assay has great scenario in food safety by using portable Raman spectrometer.

Recent progress and perspectives of metal organic frameworks (MOFs) for the detection of food contaminants

Over the past decades, increasing research in metal-organic frameworks (MOFs) being a large family of highly tunable porous materials with intrinsic physical properties, show propitious results for a wide range of applications in adsorption, separation, electrocatalysis, and electrochemical sensors. MOFs have received substantial attention in electrochemical sensors owing to their large surface area, active metal sites, high chemical and thermal stability, and tunable structure with adjustable pore diameters. Benefiting from the superior properties, MOFs and MOF-derived carbon materials act as promising electrode material for the detection of food contaminants. Although several reviews have been reported based on MOF and its nanocomposites for the detection of food contaminants using various analytical methods such as spectrometric, chromatographic, and capillary electrophoresis. But there no significant review has been devoted to MOF/and its derived carbon-based electrodes using electrochemical detection of food contaminants. Here we review and classify MOF-based electrodes over the period between 2017 and 2022, concerning synthetic procedures, electrode fabrication process, and the possible mechanism for detection of the food contaminants which include: heavy metals, antibiotics, mycotoxins, and pesticide residues. The merits and demerits of MOF as electrode material and the need for the fabrication of MOF and its composites/derivatives for the determination of food contaminants are discussed in detail. At last, the current opportunities, key challenges, and prospects in MOF for the development of smart sensing devices for future research in this field are envisioned.

A three-dimensional composite film-modified electrode based on polyoxometalates and ionic liquid-decorated carbon nanotubes for the determination of L-tyrosine in food

A stable and innovative composite film-modified electrode based on Dawson polyoxometalates H8P2Mo16V2O62 (P2Mo16V2) and ionic liquid (BMIMBr)-decorated carbon nanotubes, annotated as PEI/(P2Mo16V2/BMIMBr-CNTs)8, has been constructed by using the layer-by-layer self-assembly (LBL) method for the determination of L-tyrosine. The combination of three active components not only offers higher conductivity to facilitate rapid electron transfer, but also avoids the accumulation of P2Mo16V2 to expand the contact area and increase the reactive active sites. The modified electrode exhibits outstanding sensing performance for determination of Tyr with wide linear determination range of 5.8×10-7 M ~ 1.2×10-4 M, low determination limit of 1.7×10-7M (S/N=3), high selectivity for common interferences, and excellent stability at the potential of +0.78 V (vs. Ag/AgCl (3 M KCl)). The relative standard deviation (RSD) of 4.3% for five groups of parallel experiments shows the satisfactory repeatability of PEI/(P2Mo16V2/BMIMBr-CNTs)8. In addition, for determination of Tyr, the PEI/(P2Mo16V2/BMIMBr-CNTs)8 shows good recoveries of 98.8-99.8% in meat floss, which can be feasible in practical application.

Fabrication of a bi-metallic metal organic framework nanocomposite for selective and sensitive detection of triclosan

Transition metal-ion based nanocomposites are widely used owing to their ease of synthesis and cost-effectiveness in the sensor development. In this study, we have synthesized bi-metallic (iron and zinc) metal organic framework (MOF) nanorods-nanoparticles (denoted as Fe₂Zn-MIL-88B) with a well-defined structure and characterized them. The bimetallic material nanocomposite (Fe₂Zn-MIL-88B, nafion (Nf), and multiwalled carbon nanotube (MWCNT)) was fabricated on the electrode (glassy carbon electrode (GCE) or screen printed carbon electrode (SPCE)) surface within 10 min at room temperature. The Fe₂Zn-MIL-88B/Nf/MWCNT@GCE showed an excellent electron transfer mechanism compared to a bare GCE and bare SPCE. The Fe₂Zn-MIL-88B based nanocomposite electrode triggers the oxidation of the environmental carcinogenic molecule triclosan (TCS). Under optimized conditions, the sensor has a limit of detection of 0.31 nM and high selectivity to TCS in the presence of other interfering agents. The sensor has a good day-to-day TCS detection reproducibility. Fe₂Zn-MIL-88B was stable even after 11 months of synthesis and detected TCS with similar sensitivity. The fabrication of the Fe₂Zn-MIL-88B/Nf/MWCNT nanocomposite was successfully translated from the GCE to SPCE. TCS was detected in human plasma and commercial products such as soaps, skin care products, shampoos, and tooth pastes.

Significantly enhanced photothermal catalytic CO2 reduction over TiO2/g-C3N4 composite with full spectrum solar light

Using solar energy to drive catalytic conversion of CO₂ into value-added chemicals has great potential to alleviate the global energy shortage and anthropogenic climate change. Herein, a "hitting three birds with one stone" strategy was reported to prepared boron-doped g-C₃N₄/TiO_2-x composite (BCT) by a one-step thermal reduction process. A series of characterizations showed that the composite catalyst has extended full-spectrum absorption, rapid photogenerated charge separation, and outstanding CO₂ photoreduction performance (265.2 μmol g^-1h^-1), which is 7.5 and 9.2 times higher than that of pure TiO₂ and g-C₃N₄, respectively. In addition, the CO₂ conversion rate can be further increased to 345.1 μmol g^-1h^-1 at 70 °C due to its excellent photothermal conversion. Mechanistic studies reveal that synergistic effects alter the charge density distribution, thereby lowering the energy barrier for CO₂ conversion by adsorbing and activating CO₂ molecules_. This work provides a novel three-in-one integrated strategy for fabricating high-efficiency catalysts.

Application of oxidized multi-walled carbon nanotubes and zeolite nanoparticles for simultaneous preconcentration of codeine and tramadol in saliva prior to HPLC determination

In this work, a dispersive micro-solid phase extraction technique along with high-performance liquid chromatography-UV detection was developed for simultaneous preconcentraion and determination of trace levels of codeine and tramadol in human saliva. This method is based on the adsorption of codeine and tramadol on a mixture of oxidized multi-walled carbon nanotubes and zeolite Y nanoparticles with 1:1 ratio as an efficient nanosorbent. Various analytical parameters influencing the adsorption step including the amount of adsorbent, the pH of the sample solution, the temperature, the stirring rate, the contact time of the sample solution, and the adsorption capacity were investigated. Based on the results, 10 mg adsorbent, sample solutions with pH = 7.6, temperature of 25 °C, stirring rate 750 rpm and contact time 15 min, in the adsorption step shows the best results for both drugs. Then the effective parameters on the analyte desorption stage such as the type of desorption solution, pH of the desorption solution, desorption time and desorption volume were investigated. Studies have shown that water/methanol (50:50 v/v) as desorption solution, pH = 2.0, desorption time of 5 min and desorption volume of 2 ml gives the best results.Chromatographic separation was performed on a RP-Shim-pack CLC-ODS-C18 column (250 mm × 4.6 mm, 5 µm) with isocratic mode. The mobile phase contained of acetonitrile:phosphate buffer (18:82, v/v) at pH = 4.5 and the flow rate was 1 ml.min^-1. The wavelength of UV detector was adjusted at 210 nm and 198 nm for codeine and tramadol, respectively.Under optimum conditions, the extraction efficiencies of 98.5% and 99.2% were achieved for codeine and tramadol respectively. Enrichment factor of 13, detection limit of 0.3 μg L^-1, relative standard deviation of 4.07 for codeine; and an enrichment factor of 15, a detection limit of 0.15 μg L^-1, and standard deviation of 2.06 for tramadol were calculated. The linear range of the procedure for each drug was 1.0 to 1000 μg L^-1. This method was successfully applied for the analysis of codeine and tramadol in saliva samples.

Carbon Paper Modified with Functionalized Poly(diallyldimethylammonium chloride) Graphene and Gold Phytonanoparticles as a Promising Sensing Material: Characterization and Electroanalysis of Ponceau 4R in Food Samples

This paper presents a novel eco-friendly sensing material based on carbon paper (CP) volumetrically modified with a composite nanomodifier that includes functionalized poly(diallyldimethylammonium chloride) graphene (PDDA-G) and phytosynthesized gold nanoparticles (phyto-AuNPs). The functionalization of graphene was justified by Fourier-transform infrared spectroscopy. The phyto-AuNPs (d = 6 nm) were prepared by "green" synthesis with the use of strawberry leaf extract. The sensing material was characterized using scanning electron microscopy, electrochemical impedance spectroscopy, and voltammetry. The research results indicated a more than double increase in the electroactive surface area; a decrease in the resistance of electron transfer on nanocomposite-modified CP, compared to bare CP. The phyto-AuNPs/PDDA-G/CP was used for the electrosensing of the synthetic dye Ponceau 4R. The oxidation signal of colorant enhanced 4-fold on phyto-AuNPs/PDDA-G/CP in comparison to CP. The effect of the quantity of nanomodifier, solution pH, potential scan rate, accumulation parameters, and differential pulse parameters on the peak current of Ponceau 4R was studied. Under optimal conditions, excellent sensory characteristics were established: LOD 0.6 nM and LR 0.001-2 μM for Ponceau 4R. High selectivity and sensitivity enable the use of the sensor for analyzing the content of Ponceau 4R in food products (soft drinks, candies, and popsicles) without additional sample preparation.

Simultaneous Determination of Dopamine and Uric Acid in Real Samples Using a Voltammetric Nanosensor Based on Co-MOF, Graphene Oxide, and 1-Methyl-3-butylimidazolium Bromide

A chemically modified carbon paste electrode, based on a CoMOF-graphene oxide (GO) and an ionic liquid of 1-methyl-3-butylimidazolium bromide (CoMOF-GO/1-M,3-BB/CPE), was fabricated for the simultaneous determination of dopamine (DA) and uric acid (UA). The prepared CoMOF/GO nanocomposite was characterized by field emission-scanning electron microscopy (FE-SEM), the X-ray diffraction (XRD) method, a N₂ adsorption-desorption isotherm, and an energy dispersive spectrometer (EDS). The electrochemical sensor clearly illustrated catalytic activity towards the redox reaction of dopamine (DA), which can be authenticated by comparing the increased oxidation peak current with the bare carbon paste electrode. The CoMOF-GO/1-M,3-BB/CPE exhibits a wide linear response for DA in the concentration range of 0.1 to 300.0 µM, with a detection limit of 0.04 µM. The oxidation peaks' potential for DA and uric acid (UA) were separated well in the mixture containing the two compounds. This study demonstrated a simple and effective method for detecting DA and UA in real samples.

Enhanced artificial intelligence for electrochemical sensors in monitoring and removing of azo dyes and food colorant substances

It is necessary to determine whether synthetic dyes are present in food since their excessive use has detrimental effects on human health. For the simultaneous assessment of tartrazine and Patent Blue V, a novel electrochemical sensing platform was developed. As a result, two artificial azo colorants (Tartrazine and Patent Blue V) with toxic azo groups (-NN-) and other carcinogenic aromatic ring structures were examined. With a low limit of detection of 0.06 μM, a broad linear concentration range 0.09μM to 950μM, and a respectable recovery, scanning electron microscopy (SEM) was able to reveal the excellent sensing performance of the suggested electrode for patent blue V. The electrochemical performance of an electrode can be characterized using cyclic and differential pulse voltammetry, and electrochemical impedance spectroscopy. Moreover, the classification model was created by applying binary classification assessment using enhanced artificial intelligence comprises of support vector machine (SVM) and Genetic Algorithm (GA), respectively, a support vector machine and a genetic algorithm, which was then validated using the 50 dyes test set. The best binary logistic regression model has an accuracy of 83.2% and 81.1%, respectively, while the best SVM model has an accuracy of 90.3% for the training group of samples and 81.1% for the test group (RMSE = 0.644, R2 = 0.873, C = 205.41, and = 5.992). According to the findings, Cu-BTC MOF (copper (II)-benzene-1,3,5-tricarboxylate) has a crystal structure and is tightly packed with hierarchically porous nanomaterials, with each particle's edge measuring between 20 and 37 nm. The suggested electrochemical sensor's analytical performance is suitable for foods like jellies, condiments, soft drinks and candies.

Carbendazim imprinted electrochemical sensor based on CdMoO4/g-C3N4 nanocomposite: Application to fruit juice samples

Carbendazim (CAR) as a fungicide is utilized for fruits and vegetables to provide diseases' control and the degradation of carbendazim having benzimidazole ring is slow. Herein, a molecularly imprinted electrochemical sensor based on CdMoO₄/g-C₃N₄ nanocomposite was prepared for CAR determination in fruit juice samples. Firstly, CdMoO₄/g-C₃N₄ nanocomposite with high yield was fabricated via one-pot in-situ hydrothermal approach including environmentally friendly method. Formation of CAR imprinted polymers was performed on CdMoO₄/g-C₃N₄ nanocomposite modified glassy carbon electrode (GCE) in presence of CAR as template and pyrrole (Py) as a monomer by cyclic voltammetry (CV) technique. Following the morphological, structural, and optical characterization of as-synthesized nanocomposite, the electrochemical techniques were also implemented to evaluate the electrochemical features of fabricated electrodes. The limit of quantification (LOQ) and limit of detection (LOD) values were calculated as 0.1 × 10^-10 M, and 2.5 × 10^-12 M, respectively in addition to satisfactory selectivity, stability, reproducibility and reusability. The findings revealed that the proposed CAR imprinted electrochemical sensor can be successfully employed in food safety.

Preconcentrations of Cu (II) and Mn (II) by magnetic solid-phase extraction on Bacillus cereus loaded γ-Fe2O3 nanomaterials

For the simultaneous preconcentrations of Cu(II) and Mn(II), a novel preconcentration technique was developed and described. Bacillus cereus loaded magnetic ɣ-Fe₂O₃ nanoparticles were prepared and used as support materials on solid-phase extraction procedure. Important experimental parameters were investigated in details and pH 6.0, 3 mL min^-1 of flow rate, 5 mL of 1 mol L^-1 of HCl as eluent, 200 mg of biomass, and 200 mg of magnetic ɣ-Fe₂O₃ nanoparticles as support material was found as the best conditions. The preconcentrations factor were found to be 80 for Cu (II) and Mn(II). It was confirmed by the results that SPE columns could be used in 32 cycles. The LOD values calculated for Cu (II) and Mn (II) were 0.09 and 0.08 ng mL^-1, respectively. The RSD values found were less than 3.4%. The extraction recoveries were achieved as higher than 98%. The biosorption capacities of Cu (II), and Mn (II) were 26.0 mg g^-1, 30.3 mg g^-1 respectively. The approach devised for analyzing analyte concentrations in food samples proved to be successful.

Recent advances in Ponceau dyes monitoring as food colorant substances by electrochemical sensors and developed procedures for their removal from real samples

Ponceau dyes are one of the food coloring materials that are added to various pharmaceutical, health and food products and give them an appearance. These dyes contain contaminants such as Benzidine, 4-Aminobiphenyl, and 4-Aminoazobenzene that are safe in small amounts, but they are not approved by the US Food and Drug Administration (US-FDA) for human consumption. This study comprehensively was reviewed the properties, applications, chemistry, and toxicity of Ponceau dyes as food colorant substances. Electroanalysis of Ponceau dyes was discussed in detail, and the various electrochemical sensors used to detect and monitor these dyes as food colorant were examined. The applied methods of removing and degradation of these dyes in municipal and industrial wastes were also discussed. Conclusions and future perspectives to motivate future research were also explored.