Voltammetric determination of nitrite in meat products using polyvinylimidazole modified carbon paste electrode

Trends in pulse voltammetric techniques applied to foodstuffs analysis: The food additives detection

Food additives are chemical compounds intentionally added during foodstuff production to control technological functions, such as pH, viscosity, stability (color, flavor, taste, and odor), homogeneity, and loss of nutritional value. These compounds are fundamental in inhibition the degradation process and prolonging the shelf life of foodstuffs. However, their inadequate employment or overconsumption can adversely affect consumers' health with the development of allergies, hematological, autoimmune, and reproductive disorders, as well as the development of some types of cancer. Thus, the development and application of simple, fast, low-cost, sensitivity, and selectivity analytical methods for identifying and quantifying food additives from various chemical classes and in different foodstuffs are fundamental to quality control and ensuring food safety. This review presents trends in the detection of food additives in foodstuffs using differential pulse voltammetry and square wave voltammetry, the main pulse voltammetric techniques, indicating the advantages, drawbacks, and applicability in food analysis. Are discussed the importance of adequate choices of working electrode materials in the improvements of analytical results, allowing reliable, accurate, and inexpensive voltammetric methods for detecting these compounds in foodstuffs samples.

Nitrites in Cured Meats, Health Risk Issues, Alternatives to Nitrites: A Review

Nitrite is one of the most widely used curing ingredients in meat industries. Nitrites have numerous useful applications in cured meats and a vital component in giving cured meats their unique characteristics, such as their pink color and savory flavor. Nitrites are used to suppress the oxidation of lipid and protein in meat products and to limit the growth of pathogenic microorganisms such as Clostridium botulinum. Synthetic nitrite is frequently utilized for curing due to its low expenses and easier applications to meat. However, it is linked to the production of nitrosamines, which has raised several health concerns among consumers regarding its usage in meat products. Consumer desire for healthier meat products prepared with natural nitrite sources has increased due to a rising awareness regarding the application of synthetic nitrites. However, it is important to understand the various activities of nitrite in meat curing for developing novel substitutes of nitrites. This review emphasizes on the effects of nitrite usage in meat and highlights the role of nitrite in the production of carcinogenic nitrosamines as well as possible nitrite substitutes from natural resources explored also.

Sensitive electrochemical sensor based on nickel/PDDA/reduced graphene oxide modified screen-printed carbon electrode for nitrite detection

A simple, rapid method of the determination of nitrite in food samples is reported by using a highly sensitive electrochemical sensor based on nickel, poly(diallyldimethylammonium chloride) (PDDA), reduced graphene oxide (rGO) and a disposable screen-printed carbon electrode (SPCE). The method is based on a modification of the electrode to enhance the sensitivity and selectivity of the disposable and applicable SPCE, which is essential for the present analytical challenge. The nitrite determination was performed by using a cyclic voltammetry (CV) method under optimum conditions. Ni/PDDA/rGO/SPCE showed a linear working range of 6 to 100 μM of nitrite concentration. The limit of detection and limit of quantification were 1.99 μM (S/N = 3) and 6.6 μM (S/N = 10), respectively. The sensitivities were 0.453 μA μM^-1 cm^-2 for the lower concentration range and 0.171 μA μM^-1 cm^-2 for the higher concentration range. The Ni/PDDA/rGO sensor also showed excellent anti-interference ability and good long-term stability. The purposed disposable sensor was successfully applied to determine nitrite in sausages and pickled vegetable samples with satisfactory recovery.

Ultra-trace levels voltammetric determination of Pb2+ in the presence of Bi3+ at food samples by a Fe3O4@Schiff base Network1 modified glassy carbon electrode

In this research, a highly sensitive electrochemical sensor was developed for the square wave anodic stripping voltammetric determination of Pb²⁺ at ultra-trace levels. A Glassy carbon electrode was modified with an in-situ electroplated bismuth film and the nanocomposite of a recently synthesized melamine based covalent organic framework (schiff base network₁ (SNW₁)) and Fe₃O₄ nanoparticles (Fe₃O₄@SNW₁). The obtained results exhibit clearly that combination of Fe₃O₄@SNW₁ and in-situ electroplated bismuth film enhances the sensitivity of the modified electrode towards Pb²⁺ remarkably. A Plackett-Burman design was implemented for screening experimental factors to specify the significant variables influencing the sensitivity of the electroanalytical method. Afterward, the effective factors were optimized using Box-Behnken design (BBD). Under optimized conditions, the proposed electrode showed a linear response towards Pb²⁺ in the concentration range of 0.003-0.3 μmol L^-1 with the detection limit of 0.95 nmol L^-1. The selectivity of the fabricated electrode towards different ionic species were checked out and no serious interference was observed. At the end, the application of the designed sensor in the determination of Pb²⁺ at 10 different edible specimens were investigated and the obtained recovery values were in the range of (95.56-106.64%) indicating the successful performance of the designed sensor.

Coumarin-pyridone conjugate as a fluorescent tag for LFPs visualization and electrochemical sensor for nitrite detection

In this work, a D–π–A based coumarin–pyridone conjugate (CPC) was synthesised by a one-pot multicomponent reaction and the structure was proven from infrared and nuclear magnetic resonance spectroscopies and high-resolution mass spectrometry.

Carbon Materials in Electroanalysis of Preservatives: A Review

Electrochemical sensors in electroanalysis are a particularly useful and relatively simple way to identify electroactive substances. Among the materials used to design sensors, there is a growing interest in different types of carbon. This is mainly due to its non-toxic properties, low cost, good electrical conductivity, wide potential range, and the possibility of using it in both aqueous and nonaqueous media. The electrodes made of carbon, and especially of carbon modified with different materials, are currently most often used in the voltammetric analysis of various compounds, including preservatives. The objective of this paper is to present the characteristics and suitability of different carbon materials for the construction of working electrodes used in the voltammetric analysis. Various carbon materials were considered and briefly discussed. Their analytical application was presented on the example of the preservatives commonly used in food, cosmetic, and pharmaceutical preparations. It was shown that for the electroanalysis of preservatives, mainly carbon electrodes modified with various modifiers are used. These modifications ensure appropriate selectivity, high sensitivity, low limits of detection and quantification, as well as a wide linearity range of voltammetric methods of their identification and determination.

Film Carbon Veil-Based Electrode Modified with Triton X-100 for Nitrite Determination

A film carbon veil-based electrode (FCVE) modified with non-ionic surfactant Triton X-100 (TrX100) has been developed for nitrite determination. A new simple and producible technique of hot lamination (heat sealing) has been used for the FCVE manufacturing. The paper presents the findings of investigating the FCVE and the TrX100/FCVE by using voltammetry, chronoamperometry, and scanning electron microscopy. Modification of the electrode with TrX100 improves the hydrophilic property of its surface, which results in a larger electrode active area and higher sensitivity. Optimal conditions for nitrite determination with the use of the TrX100/FCVE have been identified. The linear range (LR) and the limit of detection (LOD) are 0.1–100 μM and 0.01 μM, respectively. The relative standard deviation (RSD) does not exceed 2.3%. High selectivity of the sensor ensures its successful application for the analysis of real samples (sausage products and natural water). The obtained results accord well with the results of the standard spectrophotometric method.

Modification-Free Fabricating Ratiometric Nanoprobe Based on Dual-Emissive Carbon Dots for Nitrite Determination in Food Samples

Great challenges still exist for facilely fabricating ratiometric fluorescent nanoprobes. Fortunately, the appearance of dual-emissive carbon dots (CDs) offers a glimmer of hope for the fabrication of modification-free ratiometric nanoprobe. The chemical and electronic structure characteristics of the dual-emissive CDs might be modulated by conjugated structures of carbon sources and the doped nitrogen and sulfur atoms, and the surface state also contributed to the fluorescence properties via surface functional groups. Herein, we report a one-pot strategy for simultaneous preparation of two kinds of CDs named RYDE CDs and RODE CDs, showing dual-emissive fluorescent peaks with long wavelength by 2,3-diaminobenzoic acid hydrochloride for the first time. Notably, trace nitrite determination with high sensitivity and selectivity was realized for the first time based on the modification-free ratiometric fluorescent nanoprobe fabricated rapidly and directly by the as-prepared RYDE CDs at constant room temperature (20 °C). Under the optimal conditions, the limit of detection for nitrite was 31.61 nM, with a wide concentration linear range of 0.1-100 μM. Furthermore, this ratiometric nanoprobe was successfully applied for nitrite analysis in bacon, sausage, pickle, and milk samples. Additionally, the nanoprobe was also capable of visually monitoring temperature fluctuations and cell imaging.

Electrochemical Biosensor for Nitrite Based on Polyacrylic-Graphene Composite Film with Covalently Immobilized Hemoglobin

A new biosensor for the analysis of nitrite in food was developed based on hemoglobin (Hb) covalently immobilized on the succinimide functionalized poly(n-butyl acrylate)-graphene [poly(nBA)-rGO] composite film deposited on a carbon-paste screen-printed electrode (SPE). The immobilized Hb on the poly(nBA)-rGO conducting matrix exhibited electrocatalytic ability for the reduction of nitrite with significant enhancement in the reduction peak at −0.6 V versus Ag/AgCl reference electrode. Thus, direct determination of nitrite can be achieved by monitoring the cathodic peak current signal of the proposed polyacrylic-graphene hybrid film-based voltammetric nitrite biosensor. The nitrite biosensor exhibited a reproducible dynamic linear response range from 0.05–5 mg L⁻¹ nitrite and a detection limit of 0.03 mg L⁻¹. No significant interference was observed by potential interfering ions such as Ca²⁺, Na⁺, K⁺, NH₄⁺, Mg²⁺, and NO₃⁻ ions. Analysis of nitrite in both raw and processed edible bird’s nest (EBN) samples demonstrated recovery of close to 100%. The covalent immobilization of Hb on poly(nBA)-rGO composite film has improved the performance of the electrochemical nitrite biosensor in terms of broader detection range, lower detection limit, and prolonged biosensor stability.

A new electrochemical sensor for highly sensitive and selective detection of nitrite in food samples based on sonochemical synthesized Calcium Ferrite (CaFe2O4) clusters modified screen printed carbon electrode

Herein, we report a novel, disposable electrochemical sensor for the detection of nitrite ions in food samples based on the sonochemical synthesized orthorhombic CaFe₂O₄ (CFO) clusters modified screen printed electrode. As synthesized CFO clusters were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformer infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and amperometry (i-t). Under optimal condition, the CFO modified electrode displayed a rapid current response to nitrite, a linear response range from 0.016 to 1921 µM associated with a low detection limit 6.6 nM. The suggested sensor also showed the excellent sensitivity of 3.712 μA μM^-1 cm^-2. Furthermore, a good reproducibility, long-term stability and excellent selectivity were also attained on the proposed sensor. In addition, the practical applicability of the sensor was investigated via meat samples, tap water and drinking water, and showed desirable recovery rate, representing its possibilities for practical application.

Carbon quantum dot-based fluorometric nitrite assay by exploiting the oxidation of iron(II) to iron(III)

The authors describe a simple and economical fluorescence method for the determination of nitrite by utilizing the fact that nitrite possesses strong oxidation in acidic solution and is capable to transform iron(II) into iron(III) ions. The latter quenches the fluorescence of carbon quantum dots (CQDs) based on the fluorescence static and dynamic quenching effect. The optimum reaction conditions and other analytical parameters are investigated to enhance the sensitivity of the method. At the excitation wavelength of 360 nm, this probe has a linear response in the 10 to 400 μM nitrite concentration range, with a correlation coefficient of R² = 0.9958 (n = 3) and a detection limit of 0.48 μM. This method was successfully applied to the determination of nitrite in three different sausage samples and gave recoveries in the range between 101.8 to 103.0%, demonstrating the accuracy, reliability and potential application of this assay for monitoring nitrite. Graphical Abstract The carbon quantum dot/iron(II) ions system was used for the fluorometric detection of nitrite in food and environmental water. This probe exploits the oxidizing property of nitrite in acidic solution. Iron(II) is oxidized to iron(III) which exerts a strong fluorescence quenching effect.

Electrochemical oxidation mechanism of eugenol on graphene modified carbon paste electrode and its analytical application to pharmaceutical analysis

Electrochemical properties of eugenol were investigated on a graphene modified carbon paste electrode (CPE) by using voltammetric methods, which exhibited a well-defined irreversible peak at about 0.7V vs Ag/AgCl, NaCl (3M) in Britton-Robinson buffer at pH 2.0. Mechanism of the electrochemical reaction of eugenol was studied by performing density functional theory (DFT) computations and mass spectroscopic analysis. (CPCM:water)-wB97XD/aug-cc-PVTZ//(CPCM:water)-wB97XD/6-31G(d) level calculations predicted that the formation of product P2, possessing a para-quinoid structure, is preferred rather than the product P1, suggested in the literature, having an ortho-quinoid system. Determination of eugenol in a pharmaceutical sample was realized in the light of the electrochemical findings, and a validated voltammetric method for quantitative analysis of eugenol in a pharmaceutical formulation was proposed. The differential pulse voltammogram (DPV) peak currents were found to be linear in the concentration range of 1.0 × 10^-7 to 1.7 × 10^-5M. The limit of detection (LOD) and the limit of quantification (LOQ) were obtained to be 7.0 × 10^-9 and 2.3 × 10^-8, respectively.

Polymer/carbon nanotubes coated graphite surfaces for highly sensitive nitrite detection

This study describes the preparation of poly(vinylferrocenium)/multi-walled carbon nanotubes (PVF(+)/MWCNTs) coated electrode and its use for sensitive electrochemical nitrite detection. PVF(+)/MWCNTs composite coated disposable pencil graphite electrode (PVF(+)/MWCNTs/PGE) was prepared by electropolymerization of poly(vinylferrocene) (PVF) in the presence of MWCNTs with one-step electropolymerization. Characterization of PVF(+)/MWCNTs/PGE was carried out with scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Then electrochemical detection of nitrite was performed using differential pulse voltammetry (DPV). Nanocomposite coated electrode showed high sensitivity to nitrite with a detection limit of 0.1 μM. The electrode platform was successfully applied to a commercial mineral water sample.

Spectrophotometric determination of nitrite in soil and water using cefixime and central composite design

The present paper seeks to develop a simple method for the spectrophotometric determination of nitrite in soil and water samples and also measure optimum reaction conditions along with other analytical parameters. The method is based on the diazotization-coupling reaction of nitrite with cefixime and 1-naphthylamine in an acidic solution (Griess reaction). The final product that is an azo dye has an orange color with maximum absorption at 360 nm which Beer's Law is obeyed over the concentration range 0.02-15.00 mg L(-1) of nitrite. Optimal conditions of the variables affecting the reaction were obtained by central composite design (CCD). A detection limit of 4.3×10(-3) mg L(-1) was obtained for determination of nitrite by the proposed method. The proposed method was successfully applied to determine nitrite in soil and water samples. The molar absorptivity of the product of the reaction and RSD in determination of nitrite in real samples are 4.1×10(3) (L mol(-1) cm(-1)) and lower than 10%, respectively.

A colorimetric nitrite detection system with excellent selectivity and high sensitivity based on Ag@Au nanoparticles

NO₂⁻ could be directly detected with high sensitivity and excellent selectivity by visualizing the color change of a dispersion of Ag@AuNPs with the unaided eye.