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.     

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.     

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.     

功能化多壁碳纳米管修饰玻碳电极测定沙丁胺醇

制备多壁碳纳米管修饰玻碳电极,应用循环伏安法研究沙丁胺醇在修饰电极上的电化学行为。结果表明,碳纳米管修饰电极对沙丁胺醇的氧化有良好的电催化活性,在最佳测试条件下,氧化峰电位负移至0.601V,比裸玻碳电极负移90mV,氧化峰电流与沙丁胺醇浓度在2.09×10-7～2.27×10-6mol/L范围内呈良好线性关系,检出限达1.9×10-7mol/L。该电极具有良好的重现性和稳定性。     

多壁碳纳米管修饰电极测定烟酰胺

研究多壁碳纳米管修饰电极的制备及其对烟酰胺的电催化检测。考察支持电解质种类、酸度和扫速等因素对烟酰胺响应的影响。在优化实验条件下,采用示差脉冲伏安法测定烟酰胺,其浓度在5.0×10-5～1.0×10-3mol/L范围内与其还原峰电流呈良好的线性关系,检出限为2.49×10-5mol/L。共存的多种离子、蔗糖、乙醇等不干扰测定。     

Simultaneous Electrochemical Determination of Caffeine and Vanillin by Using Poly(Alizarin Red S) Modified Glassy Carbon Electrode

Poly(alizarin red S) conducting polymer was prepared on glassy carbon electrode (GCE) surfaces, and the functionalized electrode was used for the simultaneous determination of caffeine (CAF) and vanillin (VAN). The peak potential separation for caffeine and vanillin was about 600 mV in 0.1 M acetate buffer solution (pH 4.0). The peak currents for the oxidation of both CAF and VAN are increased at poly(alizarin red S) (poly(ARS)) functionalized electrode, which makes it suitable for simultaneous detection of these compounds. The square wave voltanmmetry peak current of VAN was linear with the concentration of VAN from 0.5 to 250 μM in the presence of 250 μM CAF. The detection limit of VAN was found to be 0.06 μM in the presence of CAF. At the same time, the peak current of CAF was linear with the concentration of CAF from 10 to 450 μM with a detection limit of 0.8 μM (S/N = 3) in the presence of 30 μM VAN. The poly(ARS) functionalized GCE has good reproducibility and high stability. In addition, the proposed method was successfully applied to determine CAF and VAN in energy drink and vanilla sugar samples with good results.     

应用Nafion修饰电极测定油脂中过氧化物的研究

目的 探讨检测油脂中过氧化物的新方法.方法 基于食用油的介电性质,制备了Nafion修饰玻碳电极,采用循环伏安法测定食用油中的过氧化物.结果 在优化条件下,得到过氧化物浓度在3×10-6～3×10-4mol/L范围内,其浓度与峰电流线性相关.结论 得到了用Nafion修饰电极检测油脂过氧化物的新方法.     

应用Nafion修饰电极测定油脂中过氧化物的研究

目的 探讨检测油脂中过氧化物的新方法.方法 基于食用油的介电性质,制备了Nafion修饰玻碳电极,采用循环伏安法测定食用油中的过氧化物.结果 在优化条件下,得到过氧化物浓度在3×10-6～3×10-4mol/L范围内,其浓度与峰电流线性相关.结论 得到了用Nafion修饰电极检测油脂过氧化物的新方法.     

离子液体修饰玻碳电极测定金银花中的总黄酮

用1- 丁基-3- 甲基咪唑六氟磷酸盐([BMIM]PF6)疏水性离子液体作修饰剂制作[BMIM]PF6- 修饰玻碳电极。在0.2mol/L 磷酸盐缓冲液(pH7.0)中,运用差示脉冲溶出伏安法(DPSV)研究木犀草素在修饰电极上的电化学行为,建立测定金银花中总黄酮含量的新方法。研究表明,该修饰电极降低了木犀草素的氧化还原峰电位,增大了其氧化还原反应的峰电流。木犀草素氧化峰电流与其浓度在1.0 × 10-10～1.6 × 10-8mol/L 范围内呈良好的线性关系,检出限达到3.2 × 10-11mol/L,回收率为98.7%～103.6%。该法操作简单、快速、灵敏、准确,可用于金银花中总黄酮的测定。     

Square Wave Voltammetric Determination of Fomesafen Herbicide Using Modified Nanostructure Carbon Paste Electrode as a Sensor and Application to Food Samples

Cyclic and square wave voltammetric measurements were performed to deduce the electrochemical behavior of fomesafen herbicide on the prepared carbon nanotube paste electrodes. Fomesafen has created a well-defined cathodic peak at ?540 mV (vs. Ag/AgCl), but no corresponding oxidation peak has appeared on the reverse scan. The influence of the pH on the electro-reduction peak was tested at various pH values, and the E _p versus pH plot suggested that protons are involved in reduction process. Electrochemical studies showed that –NO₂ group was responsible for the reduction process. A linear relationship has been constructed in the concentration range of 0.30–40 mg/L. The limits of detection and quantification values were obtained as 0.089 and 0.297 mg/L, respectively. Fomesafen was determined in the presence of some well-known pesticides, and the extent of recoveries of 5 mg/L fomesafen in the presence of equal amounts of pesticides anilazine, pymetrozine, and triflumizole was 103.7 ± 0.9, 94.3 ± 0.4, and 97.9 ± 0.5 %, respectively (n = 3). The accuracy of the recommended method was further proved by the determination of fomesafen in spiked real samples such as apricot juice, cherry juice, and lake water with a relative error of ?4.2, ?2.8, and ?1.8 %, respectively. The obtained results suggest that the recommended method is sufficiently accurate, selective, and precise.     

Glucose Biosensor Based on a Glassy Carbon Electrode Modified with Multi-Walled Carbon Nanotubes-Chitosan for the Determination of Beef Freshness

In this study, the glucose biosensor was developed for the determination of the beef meat freshness based on a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and chitosan (Chi). Glucose oxidase (GOx) was immobilized onto the MWCNTs-Chi/GCE surface by cross-linking the enzyme through glutaraldehyde with bovine serum albumin (BSA). Glutaraldehyde solution (0.25%, w/w) was also added to prevent enzyme release. The properties of the developed biosensor were characterized with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) using [Fe (CN)₆]^3?/4?as the supporting electrolyte. The influence of various parameters was investigated, and 0.1 mol L^?1 PBS with pH = 6.4 was chosen as the optimal supporting electrolyte for this experiment. The linear relationship between the current and the concentration of glucose was obtained from 0.2 to 1.2 mmol L^?1, with a detection limit of 0.05 mM at a signal-to-noise ratio of 3 and displayed good linearity (R ² = 0.9902), while the biosensor showed a rapid response to glucose. In addition, the developed glucose biosensor was applied in the determination of glucose in beef as an indicator of beef freshness compared to the total volatile basic nitrogen (TVB-N) method. The glucose level was decreased with increasing beef storage time.     

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.     

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.     

掺杂修饰碳糊电极对蔬菜中镉的电化学快速检测

目的:本研究旨在建立一种适用于高含水蔬菜中Cd快速检测的电化学分析方法。方法:通过调整纳米氧化铝/氧化铋的掺加比进行碳糊电极的修饰优化;通过分析各基质对检测的影响,确定基质稀释比和检测条件;基于基质中主要金属元素的含量,分析了主要干扰离子的影响。结果:氧化铝/氧化铋掺杂比为20%,采用此掺杂修饰碳糊电极(DMCPE),以方波阳极溶出伏安法(SWASV)检测Cd的线性范围为0.2~70 μg/L,线性方程为:Ip=0.1774C+0.3646,相关系数r=0.9983。3种基质:黄瓜、西红柿、小白菜稀释比分别为30,60和100时,对Cd检测添加回收率为87.45%~101.14%。基质对Cd检测的影响为小白菜>西红柿>黄瓜。蔬菜中高含量的Zn2+、Mg2+对Cd的电化学检测有干扰,其中Zn2+干扰最大。SWASV法对Cd检测值可达到ICP/MS检测的87.25%~108.25%。结论:蔬菜样品经过匀浆-HNO3稀释-超声提取的前处理后,采用本研究建立的DMCPE- SWASV法可以准确快速测定其中的Cd。本研究结果为开发低成本、稳定且易操作的农产品重金属快速检测技术提供参考。     

利用3-噻吩丙二酸修饰玻碳电极快速检测苏丹红

利用电化学聚合法制备3- 噻吩丙二酸(3-TPA)修饰玻碳电极。利用循环伏安法研究苏丹红在3-TPA 修饰玻碳电极上的电化学行为,得出预富集时间、pH 值、扫描速率及扫描范围因素对该修饰电极检测苏丹红的影响。在最佳条件下,利用差分脉冲伏安法得出在2.0 × 10-5～1.3 × 10-3mol/L 浓度范围内苏丹红Ⅰ响应电流与其浓度对数呈良好的线性关系,相关系数r=0.996,检测限为4.8 × 10-6mol/L。辣椒粉、辣椒酱加标回收率分别为99.9% 和99.4%,相对标准偏差(n=3)分别为0.25% 和0.21%。另外,对苏丹红Ⅰ氧化还原机理进行了初步的探讨。     

A Simple and Efficient Electrochemical Sensor for Nitrite Determination in Food Samples Based on Pt Nanoparticles Distributed Poly(2-aminothiophenol) Modified Electrode

Pt nanoparticles were embedded into an electroactive polymer layer to modify the Au electrode and to fabricate a novel catalyst electrode. Cyclic voltammetry was performed to form the electroactive polymer, poly(2-aminothiophenol) (PATP), and deposit the Pt nanoparticles, separately. Cyclic voltammetry of the 2-aminothiophenol self-assembled monolayer on Au was conducted, and Pt nanoparticles were incorporated into film of PATP by the electrolysis of a solution of PtCl₄. Thus, newer catalyst electrode, Au/PATP-Pt_nano, was fabricated. Various analytical techniques have been used for probing the process of reduction of platinic metal precursors (X-ray diffractometer and field emission transmission electron microscope). The results indicate the presence of uniformly distributed Pt nanoparticles of the sizes d _n?=?23 nm in the Au/PATP-Pt_nano. Electroactivity of Au/PATP-Pt_nano for oxidation of nitrite was evaluated in phosphate buffer (pH 4.0). An oxidation peak at 750 mV with an enhanced peak current was observed for the oxidation nitrite. Differential pulse voltammetry studies reveal that the current response is repeatable and stable and offers a linear dependence over a wide range of nitrite concentrations from 3 μmol/L to 1 mmol/L with a detection limit of 1 μmol/L. The kinetic parameters of these process at Au/PATP-Pt_nano were calculated, i.e., k was 0.75 cm/s and (1???α)n _α was 0.52 for the nitrite oxidation. The proposed method was successfully applied in the detection of nitrite in real samples.     

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.     

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.     

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.