High Sensitive Method for Determination of the Toxic Bisphenol A in Food/Beverage Packaging and Thermal Paper Using Glassy Carbon Electrode Modified with Carbon Black Nanoparticles

A voltammetric method for fast and high sensitive determination of Bisphenol A (BPA) using glassy carbon electrode (GC) modified with carbon black nanoparticles (CB) was developed. Cyclic voltammetry study in the 0.1 M phosphates of pH = 7.0 gave single anodic peak at 578 mV. Adsorption-controlled oxidation of BPA was found to be irreversible with the participation of two electrons and two protons. The proposed CB/GC electrode significantly improved the oxidation peak current of BPA compared to the bare electrode. Under the optimum conditions, calibration curve was linear in the concentration of BPA from 0.01 to 3 × 10^?6 mol L^?1 with the detection limit of 3.4 × 10^?9 mol L^?1. Moreover, the proposed method was successfully validated by studying the recovery of BPA in commonly available samples: thermal paper (receipt, ticket) and food/beverages packaging. This paper introduces carbon black as a new, perspective material for electrode modification used in voltammetry.     

Sensitive and Simple Voltammetric Detection of Sudan I by Using Platinum Nanoparticle-Modified Glassy Carbon Electrode in Food Samples

A highly sensitive and simple voltammetric method is developed for determination of Sudan I by using platinum nanoparticles modified the glassy carbon electrode. With the optimized experimental conditions, the anodic peak currents of Sudan I are proportional to its concentration in the range of 0.002–0.3 μmol L^?1 and 0.3–7.0 μmol L^?1, and the limit of detection of 0.7 nmol L^?1 is obtained. Some dynamic parameters are also investigated in this research. This proposed method is successfully applied to the detection of Sudan I in food, such as ketchup, chili powder, duck egg yolk, and chafing dish foodstuffs, which indicates its applicability and reliability.     

Development of an Electrochemical Sensor for the Determination of Amaranth: a Synthetic Dye in Soft Drinks

The voltammetric behaviour of synthetic food colourant, amaranth, was studied using a multiwalled carbon nanotube (MWCNT) thin film-modified gold electrode in 0.1 M acetate buffer solution of pH 5.0. A well-defined oxidation peak was obtained for amaranth at 0.792 V with the modified electrode. The diffusion controlled oxidation of amaranth at the modified electrode can be attributed to the electrocatalytic nature of MWCNT, since the bare electrode has not produced an electrochemical signal under the same experimental conditions. The operational parameters such as supporting electrolyte, pH of the solution and amount of MWCNT–Nafion suspension were optimised. Under optimum conditions, the oxidation peak current varies linearly with concentration in the range from 1.0?×?10^?5 M to 1.0?×?10^?6 M with a limit of detection at 6.8?×?10^?8 M. The developed sensor has good sensitivity and selectivity towards oxidation of amaranth. The sensor was successfully employed for the determination of amaranth in three different samples of soft drinks, and the results were in good agreement with the standard spectrophotometric method.     

Electrochemical Determination of Bisphenol A at Multi-walled Carbon Nanotubes/Poly (Crystal Violet) Modified Glassy Carbon Electrode

Bisphenol A (BPA) can disrupt endocrine system. In this study, a novel and sensitive electrochemical senor based on multi-walled carbon nanotubes (MWCNTs) and poly crystal violet (PCV) modified glass carbon electrode (GCE) was developed for determination of BPA. The morphologies and properties of modified electrode were characterized by scanning electron microscopy and electrochemical impedance spectra. Compared with bare GCE and other modified electrodes, this MWCNTs/PCV/GCE exhibited an excellent electrocatalytic role for the oxidation of BPA by significantly enhancing the current response and decreasing the BPA oxidation overpotential. Under optimum conditions, the electrochemical sensor can be applied to the quantification of BPA by linear sweep voltammetry (LSV) with a linear range covering 5 × 10^?8–1 × 10^?4 mol L^?1 (with a correlation coefficient of 0.9969), and the limit detection was 1 × 10^?8 mol L^?1 (S/N = 3). The recovery was between 98.38 and 103.51% in real plastic samples. This strategy might enable more opportunities for the electrochemical determination of BPA in practical applications.     

Study on the Electrochemical Properties of Kojic Acid at a Poly(glutamic Acid)-Modified Glassy Carbon Electrode and Its Analytical Application

A poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) for the electrochemical determination of kojic acid was developed. The polymerization mechanism of glutamic acid at the glassy carbon electrode, the electrocatalytic mechanism of the poly(glutamic acid) film toward kojic acid, and the electrochemical behavior of kojic acid at the PGA/GCE were investigated. The studies revealed that the oxidation of kojic acid at the PGA/GCE is greatly facilitated, which is attributed to the weakening of the bond energy between oxygen and hydrogen due to the formation of hydrogen bond between hydroxyl group in kojic acid and the nitrogen atom in poly(glutamic acid). The oxidation of kojic acid at the PGA/GCE is a one proton–one electron process. The catalytic effect was further used to determine kojic acid by cyclic voltammetry. The oxidation peak current shows a linear relationship with the concentrations of kojic acid in the range of 8.00?×?10^?6 to 6.60?×?10^?4 mol L^?1 with the detection limit of 8.00?×?10^?7 mol L^?1. The modified electrode shows excellent sensitivity, selectivity, and stability and has been applied to detect kojic acid in a variety of food products with satisfactory results.     

Carbon Nanotube–Ionic Liquid (CNT–IL) Nanocamposite Modified Sol-Gel Derived Carbon-Ceramic Electrode for Simultaneous Determination of Sunset Yellow and Tartrazine in Food Samples

Carbon-ceramic electrode modified with multi-walled carbon nanotubes–ionic liquid (MWCNTs–IL) nanocomposite was constructed. This electrode was used for electrochemical determination of food dyes Sunset Yellow (SY) and tartrazine (Tz). The modified electrode based on high surface area and high ionic conductivity of nanocomposite exhibited electrocatalytic effect for oxidation of SY and Tz; also, oxidation peak potentials of SY and Tz effectively separated on modified electrode, and their simultaneous determination was possible. Operational parameters, such as the amount of MWCNTs in suspension, IL volume, solution pH, and scan rate, which affect the analytical performance of determination, were optimized. The present electrode behaved linearly to Sunset Yellow and tartrazine in the concentration range of 4?×?10^?7 to 1.1?×?10^?4?M and 3?×?10^?6 to 0.7?×?10^?4?M with a detection limit of 10^?7?M (0.045 mg?L^?1) and 1.1?×?10^?6?M (0.59 mg?L^?1), respectively. The proposed method was successfully utilized for simultaneous determination of SY and Tz in different food samples, and the obtained results were in good agreement to those obtained by HPLC method.     

SWCNT-modified carbon paste electrode as an electrochemical sensor for histamine determination in alcoholic beverages

In this work, a simple and rapid electrochemical method is presented for the voltammetric determination of histamine based on carbon paste electrodes bulk-modified with single-walled carbon nanotubes. As monitored in cyclic voltammetry histamine undergoes an irreversible electrochemical oxidation with a peak potential of ca. +1.25 V (vs. Ag/AgCl, 3 mol L^?1 KCl) in phosphate buffer solution (PBS, 0.1 mol L^?1, pH 6.0). At optimized differential pulse voltammetric parameters, the current response of histamine was linearly proportional to its concentration in the range from 4.5 to 720 μmol L^?1. A low limit of detection of 1.26 μmol L^?1 and a limit of quantification of 3.78 μmol L^?1 of histamine, as well as good reproducibility (RSD?=?0.48–3.40 %) were obtained using the carbon paste electrode modified with single-walled carbon nanotubes. The proposed sensor was successfully applied to the determination of histamine in commercial beer and wine samples.     

Determination of Rutin in Black Tea by Adsorption Voltammetry (AdV) in the Presence of Morin and Quercetin

This paper presents a sensitive method to rutin determination on a screen-printed multi-walled carbon nanotube electrode modified with poly(3,4-ethylenedioxythiophene) and ionic liquid (SMWCNT-PEDOT-IL). Several studies show that rutin may be absorbed onto the surface of electrodes modified with PEDOT. On the other hand, the presence of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) on the surface of the modified electrode increased the oxidation current by nearly 30 % and facilitates the oxidation of rutin to values less positive potential compared with the modified electrode only with PEDOT. Cyclic voltammetry was used to quantify and characterize the modified electrode. pH and electrochemical parameters, potential adsorption, time adsorption, and scan rate were optimized based on the oxidation of rutin to obtain the following values: pH 6.0; Eads, ?0.10 V; tads, 80 s; and scan rate 50 mV s^?1. The detection limit (3σ) was 7.7?×?10^?8 mol L^?1 and the RSD was 1.5 %. The new method was used to quantify rutin in black tea samples in the presence of others flavones with consistent results.     

Sensitive Determination of Toxic Clenbuterol in Pig Meat and Pig Liver Based on a Carbon Nanopolymer Composite

The acidified single-walled carbon nanotubes (SWCNTs) were self-assembled on graphene oxide (GO) and then ultrasonically dispersed in a copolymer, Nafion solution, to form a GO/SWCNTs-Nafion polymer nanocomposite, which was employed to modify glassy carbon electrode (GCE). The surface morphological characteristics of different modified electrodes including bare GCE, GO-Nafion/GCE, and GO/SWCNTs-Nafion/GCE were imaged by scanning electron microscopy. For comparison, the differential pulse voltammetry and cyclic voltammetry behaviors were investigated, showing that the GO/SWCNTs-Nafion polymer composite has strong enhancement effect towards oxidation of clenbuterol (CLB). And the corresponding mechanism has been well discussed. During the reaction process, the anilino group of CLB molecule (1) was firstly oxidized to form a radical cation (2), exhibiting a characteristic oxidation peak (I) at 0.95 V, then two radical cations reacting via head-to-head coupling to form a diphenylamine intermediate (3), which was transformed into a CLB dimmer (4) through an azo bond by intramolecular electrons transferring under low potential, exhibiting a pair of reversible oxidation peak (II) and reduction peak (III). Under the optimum conditions, the composite modified electrode showed linear response to CLB in a concentration range of 1.0 × 10^?8~6.0 × 10^?6 mol/L with a detection limit of 6.0 × 10^?9 mol/L. The modified electrode possessed good selectivity, reproducibility, and stability. In comparison with two routine analytical methods like ELISA kit and high-performance liquid chromatography (HPLC), the electrode can be successfully applied to determination of content of CLB in pig meat and pig liver samples with a recovery rate of 96.4~104.2%, suggesting a promising application in food security field.     

A simple gold plate electrode modified with Gd-doped TiO2 nanoparticles used for determination of trace nitrite in cured food

A simple gold plate electrode (GPE) based on a gadolinium-doped titanium dioxide (Gd/TiO₂) ultrathin film was successfully constructed by using a surface sol-gel technique, and used for the detection of trace amounts of nitrite in cured foods. The Gd/TiO₂ nanoparticles were synthesised and characterised via scanning electron microscopy (SEM) and X-ray diffraction (XRD), indicating that the Gd-doped TiO₂ formed an anatase phase through roasting at 450°C, generating actively interstitial oxygen at the interface of the surface of TiO₂ lattice surrounded by Gd³⁺. The electro-catalytic effect for oxidation of nitrite on the modified electrode was investigated by cyclic voltammetry in 0.10?mol?l^?1 sulfuric acid media solution, showing that the modified electrode exhibited excellent response performance to nitrite with good reproducibility, selectivity and stability. The catalytic peak current was found to be linear with nitrite concentrations in the range of 8.0?×?10^?7 to 4.0?×?10^?4??mol?l^?1, with a detection limit of 5.0?×?10^?7?mol?l^?1 (S/N?=?3). The modified electrode could be used for the determination of nitrite in the cured sausage samples with a satisfactory recovery in the range of 95.5–104%, showing its promising application for food safety monitoring.     

Application of ZnO/CNTs Nanocomposite Ionic Liquid Paste Electrode as a Sensitive Voltammetric Sensor for Determination of Ascorbic Acid in Food Samples

In this study, a simple and rapid analytical method development for ascorbic acid (AA) determination in food samples by using differential pulse voltammetry (DPV) method on ZnO/CNTs nanocomposite ionic liquid modified carbon paste electrode. For this, several parameters, such as ZnO/CNTs nanocomposite, ionic liquid ratio, and pH, have been studied. The cyclic voltammogram showed an irreversible oxidation peak at 0.61 V (vs. Ag/AgCl_sat), which corresponded to the oxidation of AA. Compared to common carbon paste electrode, the electrochemical response was greatly improved. Under the optimized conditions, the oxidation peak current of AA showed linear dynamic range 0.1–450 μmol l^?1 with a detection limit of 0.07 μmol l^?1, using the DPV method. The proposed sensor was successfully applied to the determination of AA in fresh vegetable juice, fruit juices and food supplement samples without previous preparation and was compared with a published electrochemical method.     

Sensitive and Selective Determination of Riboflavin in Food and Pharmaceutical Samples Using Manganese (III) Tetraphenylporphyrin Modified Carbon Paste Electrode

A chemically modified electrode was constructed by incorporating manganese (III) tetraphenyl porphyrine into a carbon paste matrix. The modified electrode was used as a sensitive electrochemical sensor for measuring of riboflavin. The constructed electrode exhibited catalytic properties for the electro-oxidation of riboflavin and lowered the over potential for the oxidation of this compound; consequently, the corresponding peak currents of riboflavin increased significantly. The modified electrode showed a near-Nernstian behavior for electro-oxidation of riboflavin hence, it could be a suitable voltammetric sensor for the fast and easy determination of riboflavin. A linear response in concentration range 1.0 × 10^?8 – 1.0 × 10^?5 M was obtained with a detection limit of 8.0 × 10^?9 M (S /n = 3) for the determination of riboflavin. The electrode showed long-term stability and the standard deviation of the slope obtained after repeated calibration during a period of 3 months was 3.5% (n = 10). The modified electrode was used for differential pulse voltammetric determination of riboflavin in pharmaceutical and food samples.     

Sensitive and Selective Determination of Riboflavin in Milk and Soymilk Powder by Multi-walled Carbon Nanotubes and Ionic Liquid [BMPi]PF<Subscript>6</Subscript> Modified Electrode

A novel electrochemical method to detect riboflavin was proposed using a multi-walled carbon nanotubes and ionic liquid N-butyl-N-methyl-piperidinium hexafluorophosphate composite film modified glassy carbon electrode (MWNTs-[BMPi]PF₆/GCE). A well-defined CV behavior with a pair of sensitive and well-shaped redox peak was observed, and the response value of riboflavin at MWNTs-[BMPi]PF₆/GCE is much higher than that at MWNTs/GCE in 0.1 mol L^?1 HAc-NaAc buffer solution (pH 4.5). The electrochemical approach based on a sensitive DPV analytical signal exhibits an excellent analytical performance with a wide linear range (2.6 × 10^?8 to 1.3 × 10^?6 mol L^?1) and low detection limit (4.7 × 10^?9 mol L^?1) for the riboflavin. Moreover, the proposed method possesses a potential practical application value and can be employed for the quantitative analysis of trace riboflavin with a recovery of 95.8–102.4 % in food samples such as milk and soymilk powder.     

Electrochemical detection of pyrosine with electrochemically reduced graphene oxide modified glassy carbon electrode

Pyrosine detection and quantification was reported by voltammetry with the electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE). The differential pulse voltammograms of pyrosine on the modified GCE showed that pyrosine can be sensitively detected, which may be attributed to the large surface area of ERGO and the improved electron transfer ability of ERGO compared to graphene oxide. The effect of supporting electrolyte and its concentration on the detection of pyrosine was also investigated in this paper. The ERGO modified GCE showed a linear concentration range between 1.6 and 374 μmol L^?1 of pyrosine with a correlation coefficient of 0.9972, and the detection limit was as low as 1.2 × 10^?8 mol L^?1 (signal-to-noise ratio of 3).     

Electrochemical determination of Sudan I using montmorillonite calcium modified carbon paste electrode

In the current work, a sensitive, rapid and convenient electrochemical method was developed for the determination of Sudan I utilizing the excellent properties of montmorillonite calcium (MMT-Ca). Compared with the unmodified carbon paste electrode (CPE), MMT-Ca modified CPE not only significantly enhances the oxidation peak current of Sudan I but also lowers the oxidation overpotential, suggesting that the MMT-Ca modified CPE can remarkably improve the determining sensitivity of Sudan I. The experimental conditions such as determining medium, the content of MMT-Ca and accumulation time were optimized for the determination of Sudan I. The oxidation peak current is proportional to the concentration of Sudan I over the range from 0.05 mg L⁻¹ (2.01 × 10⁻⁷ mol L⁻¹) to 1.0 mg L⁻¹ (4.03 × 10⁻⁶ mol L⁻¹), and the limit of detection is 0.02 mg L⁻¹ (8.06 × 10⁻⁸ mol L⁻¹) for 2-min accumulation. Finally this newly-proposed sensing method was successfully employed to detect Sudan I in practical samples and good recovery was achieved.     

Potentiometric Determination of Aluminum in Foods, Pharmaceuticals, and Alloys by AlMCM-41-Modified Carbon Paste Electrode

A new chemically modified electrode is constructed by incorporating AlMCM-41 into carbon paste matrix (AlMCM-41-MCPE) and used as a sensitive sensor for detection of aluminum in aqueous and nonaqueous solutions. The rapid exchange kinetics in the membrane results in a near-Nernstian behavior of the modified electrode and makes it a suitable potentiometric sensor for detection of aluminum. A linear response in concentration range from 1.0?×?10^?6 to 1.0?×?10^?1 mol/L (0.027 μg/mL–2.7 mg/mL) was obtained with a detection limit of 4.6?×?10^?7 mol/L for the potentiometric detection of aluminum. Selectivity coefficients of a number of interfering cations have been estimated. The interference from many of the investigated ions is negligible. The AlMCM-41-MCPE is suitable for use in aqueous solution of pH 2–6 and in partially nonaqueous medium. The modified electrode exhibited a fast response time (~8 s), good stability, and an extended lifetime. The developed sensor was used successfully for the determination of Al³⁺ in some alloys, drugs, and food products.     

Selective Determination of Selenium in Garlic, Mushroom and Water Samples by Chemically Modified Mesoporous Silica Solid Phase Coupled with ICP-OES

A selective sorbent for solid phase extraction (SPE), based on a chemically modified mesoporous silica (SBA-15), followed by inductively coupled plasma-optical emission spectrometry was used for extraction, preconcentration, and determination of selenium in water and food samples. The main parameters of SPE including pH, amount of mesoporous (solid phase), concentration of the eluent (desorption solvent), and equilibrium time were optimized by using a fractional central composite design (f-CCD). The optimum conditions were found to be 3.2 for pH, 21 mg for amount of the mesoporous, 1 mol l^?1 for eluent concentration, and 9 min for equilibrium time. Under the optimal conditions, the limit of detection (LOD) was 2.56 μg l^?1. The linear dynamic range (LDR) was 5–1,000 μg l^?1 with determination coefficient (R ²) of 0.999. Relative standard deviation (C?=?400 μg l^?1, n?=?5) was 3.84 %. The enrichment factor was 20. The maximum sorption capacity of the modified SBA-15 was 15 mg g^?1. The sorbent presented good stability, reusability, high adsorption capacity, and fast rate of equilibrium for sorption/desorption of selenium (IV) ions.     

ZnO Nanoparticle Ionic Liquids Carbon Paste Electrode as a Voltammetric Sensor for Determination of Sudan I in the Presence of Vitamin B<Subscript>6</Subscript> in Food Samples

Room-temperature ionic liquid n-hexyl-3-methylimidazolium hexafluoro phosphate as a binder and ZnO nanoparticle (ZnO/NPs) as a sensor were used to construct a new ZnO/NPs carbon ionic liquid paste electrode (ZnO/NPs/IL/CPE), which exhibited enhanced electrochemical behavior as compared with the traditional carbon paste electrode with paraffin for electrooxidation of Sudan I. This modified electrode exhibited a potent and persistent electron mediating behavior followed by well separated oxidation peaks of Sudan I and vitamin B₆. The peaks current of square wave voltammograms (SWV) of Sudan I and vitamin B₆ increased linearly with their concentration in the ranges of 0.01–400 μM Sudan I and 0.5–800 μM vitamin B₆. The detection limits for Sudan I and vitamin B₆ were 0.008–0.2 μM, respectively. The modified electrode has been successfully applied for the assay of Sudan I and vitamin B₆ in food samples.     

Electrochemical Determination of Tert-Butyl Hydroquinone in Edible Oil Samples at Poly (Crystal Violet) Modified Glassy Carbon Electrode

The synthetic phenolic antioxidant tert-butyl hydroquinone (TBHQ) is frequently associated to adverse health effects. A polymerized film of crystal violet (CV) was prepared on the surface of a glass carbon electrode (GCE) by electropolymerization in alkaline solution, and then the modified electrode was successfully used to determine TBHQ. This electrode was characterized by scanning electron microscopy and electrochemical impedance spectra. The voltammetric behavior of TBHQ over an extended pH range using cyclic voltammetry at poly (crystal violet) modified glassy carbon electrode (PCV/GCE) was also studied. The resulting electrode exhibited excellent electrocatalytic activity towards the oxidation of TBHQ, and this was confirmed by the observed increased redox peak currents and shifted potentials. The electrochemical sensor can be applied to the quantification of TBHQ with a linear range covering 5?×?10^?7–1?×?10^?4 mol?·?L^?1 (with a correlation coefficient of 0.9969) and the limit detection was 3?×?10^?8 mol?·?L^?1(S/N?=?3). The recovery was between 97.1 and 102 % in edible oil samples. The electrochemical sensor method was also compared with a HPLC method, which proves its capability in commercial market surveillance.     

Electrochemical Determination of Phoxim in Food Samples Employing a Graphene-Modified Glassy Carbon Electrode

Employing a graphene-modified glassy carbon electrode, a sensitive and convenient electrochemical method for the determination of phoxim by linear sweep voltammetry was developed. The electrochemical behavior of phoxim at the modified electrode was studied by cyclic voltammetry. In citric acid–phosphate buffers, the modified electrode exhibited excellent electrocatalytical effect on the reduction of phoxim and this was further used for the determination of phoxim. Under optimized analytical conditions, the reduction peak current showed a linear relationship with the concentration of phoxim in a range of 5.97 to 5,966 μg L^?1, with a correlation coefficient of 0.9993 and a detection limit of 2.39 μg L^?1. The proposed method shows excellent sensitivity, selectivity, and linearity and has been successfully applied for the determination of phoxim in a variety of food samples with satisfactory results.