Electrochemical Behaviors of 2-Amino-3-Hydroxypyridine onto the Glassy Carbon Sensor Electrode: Simultaneous and Independent Determinations of Quercetin, Galangin, 3-Hydroxyflavone, and Chrysin

Flavonoids, with high antioxidant activity in fruits and vegetables, are natural vegetable dyes synthesized from phenylalanine. They are very essential for human health due to their activity as free radical acceptors. In this paper, the availability in the determination of quercetin (Que), galangin (Gal), 3-hydroxyflavone (3HF), and chrysin (Chr) of a modified glassy carbon (GC) sensor electrode using 2-amino-3-hydroxypyridine (AHP) was examined separately and simultaneously by cyclic voltammetry (CV). Surface characterization of modified electrodes was performed using CV, electrochemical impedance spectroscopy, and scanning electron microscopy techniques. The modification of AHP onto the GC electrode surface was carried out between ?150 and +600 mV potential range using 100 mV?s^?1 scanning rate with 30 cycles. The binding of flavonoid derivatives onto the modified surface was performed between +300 and +1,700 mV potential range using 100 mV?s^?1 scanning rate with 10 cycles. The usability of the modified electrode was examined in the determination of some flavonoids by square wave voltammetry. From the experimental results, it was found out that Que, 3HF, and Chr; Gal, 3HF, and Chr; and 3HF and Chr can be determined simultaneously by using an AHP-modified GC sensor electrode. Also, these molecules can easily be determined separately by using the modified electrode.     

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.     

A novel sensitive electrochemical method for the detection of ractopamine in meat food via polycitrulline-modified electrode

ABSTRACT

In this paper we report the modification with citrulline of the surface of a glassy carbon electrode (GCE) through cyclic voltammetry to prepare a polycitrulline-modified electrode (PCit/GCE). The electrochemical behaviour of ractopamine on this PCit/GCE was then investigated by cyclic voltammetry, to establish a novel electrochemical method for the detection of ractopamine residues in animal tissue. The optimum preparation conditions for the modified electrode were found to include a polymerisation solution pH of 6.8. The cyclic voltammetry required 12 scan cycles at a scan rate of 40 mV/s with a potential range of ?1.6 to 2.3 V. The optimum conditions to determine ractopamine were in a solution of pH 6.0 with cyclic voltammetry performed at a scan rate of 60 mV/s and a potential range of 0.4 to 1.0 V. To analyse meat, the tissue sample was extracted with ethanol, filtered, evaporated to dryness and diluted with phosphate buffered saline at pH of 6.0 before being analysed in the electrochemical cell. The limit of detection of the new method for ractopamine was 1.0 ng/g and the correlation coefficient (R) was 0.9991 in the concentration range of 140–5410 ng/g. Ractopamine residue levels in spiked beef and mutton samples were detected by the modified electrode and the recovery was in the range of 96%-101%, giving results consistent with a validated HPLC method. This study provides a new method for detection and quantification of ractopamine residues in animal tissue.     

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.     

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.     

Analysis of sudan I,sudan II,sudan III,and sudan IV in food by HPLC with electrochemical detection: Comparison of glassy carbon electrode with carbon nanotube-ionic liquid gel modified electrode

A method was developed for analyzing of sudan I, sudan II, sudan III, and sudan IV by high performance liquid chromatography coupled with an electrochemical detector. The electrochemical oxidation of each compound was investigated with a carbon nanotube-ionic liquid gel modified glassy carbon (MWNTs-IL-Gel/GC) electrode using cyclic voltammetry. The results were compared with those of glassy carbon electrodes. At the MWNTs-IL-Gel/GC electrode, highly reproducible, well-defined cyclic voltammograms for sudan oxidation were obtained. In the flow system, MWNTs-IL-Gel/GC exhibited highly reproducible and well-defined amperometric signals without peak tailing. In addition, the determination of sudan dyes by mean of isocratic reverse-phase HPLC, with amperometric detection at MWNTs-IL-Gel/GC and GC electrode, have been investigated. The chromatograms showed excellent separation. The detection limits ranged from 0.001 to 0.005 ppm. The method was sensitive, selective and could be applicable for the assay of sudan dyes in soft drink samples.     

Electrochemical Properties of MDA/GC Electrode and Investigation of Usability as Sensor Electrode for Determination of Que, Kae, Lut and Gal Using CV, DPV and SWV

Flavonoids, natural vegetable dyes synthesized from phenylalanine, are responsible for the colour of blooming portions of plants. They are very essential for human health due to their activity as free radical acceptors. In this study, electrochemical modification of a glassy carbon (GC) electrode with 4,4′-methylenedianiline (MDA) was carried out, and the modified electrode was investigated separately and simultaneously for the availability in determination of quercetin, kaempferol, luteolin and galangin. The surface modification of the GC electrode was performed with MDA using cyclic voltammetry (CV), whereas the characterization of this sensor electrode was performed using CV, electrochemical impedance spectroscopy and scanning electron microscopy. The usability of the modified electrode has been examined in the determination of some flavonoids using CV, differential pulse voltammetry and square wave voltammetry. Consequently, flavonoid derivatives can easily be determined separately and simultaneously by using an MDA-modified GC sensor electrode.     

A Novel Electrochemical Sensor Based on Graphene Oxide Decorated with Silver Nanoparticles–Molecular Imprinted Polymers for Determination of Sunset Yellow in Soft Drinks

In this study, a new imprinted electrochemical sensor for selectively detecting sunset yellow was developed based on glassy carbon electrode (GCE) modified by graphene oxide decorated with silver nanoparticles–molecular imprinted polymers (GO/AgNPs–MIPs). GO/AgNPs were firstly synthesized using self-assembly technology, and GO/AgNPs–MIPs were synthesized through surface imprinted technology by using GO/AgNPs as the substrate and sunset yellow as the template, respectively. The sensor was prepared by a drop-casting method. The synthetic materials were characterized by transmission electron microscope (TEM), Fourier transmission infrared spectra (FT-IR), and X-ray diffraction (XRD). The sensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The usage amount of GO/AgNPs–MIPs suspensions, solution pH, and accumulation time made an important difference in the process of detecting sunset yellow. Under optimal conditions, the peak current is linear to concentration of sunset yellow in the ranges of 0.1–0.6 and 0.6–12 μM, and the limit of detection was estimated to be 0.02 μM (S/N = 3). Finally, the proposed sensor was applied to detect sunset yellow in soft drinks with acceptable recovery, which demonstrated that the sensor could be used as a reliable and simple method for practical detection of sunset yellow.     

Sensitive and Efficient Electrochemical Determination of Kojic Acid in Foodstuffs Based on Graphene-Pt Nanocomposite-Modified Electrode

A differential pulse voltammetric (DPV) method for the determination of kojic acid was developed. Glassy carbon (GC) electrode was modified with composite nanomaterials of graphene (GR) sheets and platinum (Pt) nanoparticles. Electrochemical behavior of kojic acid on the electrode was studied, which indicated that the nanocomposite-modified electrode could efficiently promote electrocatalytic oxidation of kojic acid based on synergistic effect of excellent electrical conductivity and high catalytic activity of GR and Pt. A rapid, sensitive, and simple electrochemical method was then developed for determination of kojic acid using the constructed electrode. Under the optimized conditions, the oxidation peak current exhibited a wide linear range from 0.2 to 1,000 μM towards the concentration of kojic acid with a sensitivity of 139.3 μA mM^?1, and the limit of detection was as low as 0.2 μM. The modified electrode was also used for quantitative analysis of kojic acid in food samples, and the recoveries were between 97.5 and 101.3 %, indicating feasibility of the electrochemical method for kojic acid analysis in routine detection. In view of optimization and validation results as well as applicability to real samples, this method could be considered as a good alternative for routine analysis of kojic acid in foodstuffs.     

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.     

A Simple and Sensitive Method for the Voltammetric Analysis of Theobromine in Food Samples Using Nanobiocomposite Sensor

Theobromine (TB) is one of important natural methylxanthine alkaloids in plants and their products, but there were few reports on the electrochemistry of TB, especially electrochemical measurements using chemically modified electrode owing to its poor detectability. In this work, a simple and sensitive method for the voltammetric analysis of TB in green tea, chocolate, and coffee samples was successfully realized using nanobiohybrid sensor based on glassy carbon electrode (GCE) modified by both carboxyl-functionalized multiwalled carbon nanotubes (fMWCNTs) and soluble biopolymer sodium salt of carboxymethylcellulose (CMC). Water-dispersible nanonbiohybrids with fMWCNTs were successfully prepared using CMC assist, and CMC-fMWCNTs were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscope, electrochemical impedance spectroscopy, and cyclic voltammetry. CMC-fMWCNTs/GCE showed enlarged electrochemically active surface area, good electrode stability, and enhanced electrocatalytic activity. The voltammetric behavior of TB demonstrated an irreversible electrochemical oxidation reaction involving two electrons and two protons, which could detect TB in a wider linear range from 0.5 to 80 μM with a lower limit of detection (LOD) of 0.21 μM. The developed method displayed a high sensitivity, low LOD, good sensing stability, remarkable feasibility, and satisfactory practicality.     

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.     

纳米金/氧化石墨烯—离子液体修饰电极测定多菌灵

制备带正电的氧化石墨烯—离子液体(GO-IL)复合材料,用带负电的纳米金(GNP)自主装到GO-IL表面,构建GNP/GO-IL/GC修饰电极。利用电化学阻抗谱对所制备的修饰电极进行表征,在0.2～10μmol/L浓度范围内,多菌灵的差分脉冲伏安峰电流与浓度呈现良好的线性关系,相关系数R为0.997,检出限为0.08μmol/L。并用差分脉冲伏安法对砂糖橘中多菌灵含量进行了测定,结果表明,该方法简便、快捷、灵敏度高。     

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.     

Simple Voltammetric Determination of Rhodamine B by Using the Glassy Carbon Electrode in Fruit Juice and Preserved Fruit

This paper reported an innovative simple voltammetric approach for determination of rhodamine B based on a glassy carbon electrode. Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical behavior of rhodamine B. After optimizing the experimental conditions, the anodic peak current of rhodamine B was linear to its concentration in the range of 4.78–956.1 μg?L^?1, and the limit of detection was 2.93 μg?L^?1 in pH 4.0 buffer solution. The electrode showed good repeatability and acceptable selectivity. This method was successfully applied to the detection of rhodamine B in preserved fruit and fruit juice samples, which has shown good reliability.     

钴酞菁与碳纳米管共修饰碳纤维织物传感器的制备及其电化学性能

为探索钴酞菁(CoPc)/碳纳米管(CNT)柔性葡萄糖传感器在葡萄糖检测中的应用,制备了一种CoPc和CNT共修饰的柔性碳纤维织物(CFT)修饰电极,并利用电化学工作站的银/氯化银参比电极和铂对电极与其共同组成三电极体系的葡萄糖传感器。借助扫描电子显微镜对修饰电极进行表征,采用循环伏安法、电化学阻抗图谱法、时间-电流曲线法研究葡萄糖传感器的电化学性能。结果表明:该修饰电极具有良好的导电性和电子转移能力,葡萄糖检测线性范围为4×10^-3~2.6 mmol/L,检测限为1.4 μmol/L (信噪比为3),灵敏度为231 μA·L/mmol;该修饰电极在检测葡萄糖时具有较好的重复性,测试10次后其响应电流仍可达到初始值的94.6%,且对果糖、蔗糖、乳糖、半乳糖、抗坏血酸、多巴胺、尿酸等物质具有较强的抗干扰性能。     

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.     

Amperometric Determination of Quercetin in Some Foods by Magnetic Core/Shell Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@ZnO Nanoparticles Modified Glassy Carbon Electrode

In this paper, Fe₃O₄@ZnO core/shell magnetic nanoparticles (MNPs) have been synthesized by a simple method, to modify carbon paste/glassy carbon electrode and improve its efficiency for determination of quercetin. The synthesized MNPs were characterized by X-ray powder diffraction (XRD), transmission electronic microscope (TEM), and scanning electronic microscope (SEM). SEM and TEM results show that the prepared Fe₃O₄@ZnO MNPs are made of the spherical shape particles with an average size of about 15 nm. The electrochemical behavior of quercetin at the surface of modified electrode was investigated. Under the optimal conditions, a linearity range of quercetin was 7.9?×?10^?7 to 6.1?×?10^?5 mol/L (0.24–18.44 mg/L) with detection limit (S/N?=?3) and sensitivity of 0.16 μmol/L (0.048 mg/L) and 0.04 μA/μM, respectively. The validated method was applied successfully for determination of quercetin in some foods and human breast milk.     

基于多壁碳纳米管修饰四氧化三钴传感器检测白菜中杀螟硫磷

目的 基于多壁碳纳米管修饰四氧化三钴(Co3O4@MWCNTs)纳米复合物,成功构建了一种用于白菜样品中快速检测杀螟硫磷的电化学传感器。方法 将以醋酸钴水合物为钴源,而采用简便水热法制备的四氧化三钴纳米颗粒与多壁碳纳米管复合成Co3O4@MWCNTs纳米材料,以Co3O4@MWCNTs纳米复合物修饰的玻碳电极(GCE)为工作电极,利用循环伏安法(CV)研究了杀螟硫磷在修饰电极界面的电化学行为;并通过逐步优化支持电解质的PH值、复合材料质量比等检测条件。结果 实验结果表明,Co3O4@MWCNTs/GCE改性电极能够实现对杀螟硫磷的灵敏检测。在最优条件下,该传感器的线性浓度范围为1.0×10-5~1.4×10-4 mol/L,R2=0.991,检出限为7.8×10-8 mol/L(S/N=3);并成功用于实际白菜样品中杀螟硫磷的加标回收实验,回收率为93.7%~97.6%。结论 Co3O4和MWCNTs复合后制备的传感器不仅可以选择性识别杀螟硫磷,达到快速检测目标物的需求。而且,其电化学性能也得到了明显的提升,展现出较高的灵敏度,表明该传感器在现场检测中具有非常大的应用潜力。     

An Electrochemical Nanosensor for Simultaneous Voltammetric Determination of Ascorbic Acid and Sudan I in Food Samples

In this work, we describe application of a high-sensitive electrochemical sensor for determination of ascorbic acid (AA) in the presence of high concentration of Sudan I in food samples. In the first step, we study synthesis and characterization of NiO/NPs with X-ray diffraction (XRD) method. In the second step, application of NiO/NPs describe in the preparation of carbon-paste electrode modified with (9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)-4-ethylbenzene-1,2-diol (DEDED) as a high-sensitive and selective voltammetric sensor for determination of AA and Sudan I. The electrocatalytic oxidation of AA at the modified electrode was investigated by cyclic voltammetry, chronoamperometry and square wave voltammetry (SWV). For the mixture containing AA and Sudan I, the peaks potential was well separated from each other. Their square wave voltammetrics peaks current increased linearly with their concentration at the ranges of 0.01–600 and 0.5–1,000 μM, with the detection limits of 0.006 and 0.2 μM, respectively. Finally, the proposed method was also examined as a selective, simple, and precise electrochemical sensor for the determination of AA and Sudan I in real samples such as fruit juices, fresh vegetable juice, chilli sauce and tomato sauce.