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.     

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.     

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。     

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.     

Disposable Electrochemical Ascorbic Acid Sensor Based on Molecularly Imprinted Poly(o-phenylenediamine)-Modified Dual Channel Screen-Printed Electrode for Orange Juice Analysis

An electrochemical biomimetic sensor was developed for fast and selective detection of ascorbic acid (AA) in orange juice samples via electropolymerizing o-phenylenediamine on the surface of a dual channel screen-printed carbon electrode (SPCE), which could achieve two repetitive measurements by using the same sample drop and improve test efficiency. The square wave voltammograms and scanning electron microscopy images indicated that the many imprinted cavities had formed in the AA-imprinted poly(o-phenylenediamine) film, which acted as a selective recognition element to determine AA by means of the matched size, shape, and orientation of the functional groups between the imprinted cavities and AA molecules. The response current of the imprinted sensor was linearly related to the concentration of AA in both lower concentration regions (0.45–13.52 μM) and higher concentration regions (13.52–409.10 μM), respectively. The detection limit was 0.11 μM based on the signal to noise ratio of 3. The sensor was applied to determine AA in commercial orange juice, and the result was in good agreement with that obtained by 2,6-dichlorophenol indophenol titration method. The fabrication of the sensor was simple and timesaving (<35 min for modifying two work electrodes). Together with portability and disposability of the AA-MIP/SPCE, the proposed sensor had widely potential applications in field test and analysis.     

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.     

聚谷氨酸的微生物法制备及其水凝胶应用简介

研究中分离得到1株产聚谷氨酸(PGA)的芽孢杆菌,对菌种进行了分类鉴定,包括生理生化实验、Bi-olog-System4.20和16S rRNA基因序列分析,将其命名为Bacillus licheniformisNK-03。对该菌产聚谷氨酸的发酵条件进行了优化,发酵合成PGA的产率为11g/L。PGA溶液经60Co-γ射线照射后形成的水凝胶有很强的吸水性,可吸收2000倍以上体积的水分。     

黑液铝沉木质素@PAN基碳纤维电极材料电化学性能及其超级电容器应用研究

采用硫酸铝胶体沉淀分离竹浆黑液高分子质量木质素,得到铝沉木质素（AlpL）,以AlpL和聚丙烯腈（PAN）为原料,采用静电纺丝法-预氧化-碳化路线,制备了电化学性能良好的AlpL@PAN基碳纤维并研究其作为超级电容器电极材料的电化学性能。当AlpL占比为60%时,AlpL@PAN基碳纤维表现出最好的电容性能和较好的循环稳定性;其内部电阻值达1.138Ω,循环1000次后仍能保留94.50%的电容。     

木质素基凝胶电极材料的组装及其电化学性能研究

本研究以木质素磺酸钠(LS)为功能分子,氧化石墨烯(GO)为模板,在80℃温和条件下通过一步水热法制备木质素/石墨烯复合水凝胶(LGH),并以此为自支撑的电极材料直接组装超级电容器,测试其电化学性能。通过扫描电子显微镜(SEM)、元素分析仪(EA)、傅里叶变换红外光谱仪(FT-IR)等测试和表征了LGH的微观形貌和结构组成。通过循环伏安法(CV)、恒流充放电循环法(GC)和电化学阻抗谱(EIS)测试其电化学性能。研究表明,LGH具有相互贯穿的网络结构,且木质素磺酸钠成功修饰于LGH的网络结构中。电化学测试结果表明,电流密度为1 A/g时,LGH在1 mol/L的HClO_4电解液中具有优异的质量比电容(140 F/g),为单纯石墨烯凝胶(81 F/g)的1.73倍,且该器件在电流密度20 A/g下表现出较高的倍率性能(74.3%)。     

酸掺杂聚苯胺电极材料的制备及其电化学性能研究

本研究以苯胺为单体,过硫酸铵为氧化剂,植酸为掺杂酸,与木质素磺酸盐进行化学聚合,通过原位化学氧化法合成了电子传导能力良好和电容性能优异的木质素磺酸盐/聚苯胺（LS/PANI）电极材料,采用场发射扫描电子显微镜（FESEM）、傅里叶变换红外光谱仪（FT-IR）和比表面积及孔径分析仪（BET）对LS/PANI电极材料进行分析表征;运用循环伏安、充放电、电化学阻抗等测试LS/PANI电极材料电化学性能。结果表明,LS/PANI电极材料具有良好的电容性能和较好的循环稳定性;在充放电0.5 A/g的电流密度下比电容可以达到509.3 F/g,在充放电电流密度为10 A/g时,循环5 000次后仍能保留63.23%的电容。     

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.     

铜盐辅助木质素基碳气凝胶的快速制备及其电化学性能研究

本研究提出了一种铜盐辅助纳米木质素基气凝胶的快速合成方法,实现了具有显著微孔特征和三维（3D）互联结构的碳气凝胶制备。以绿色低共熔溶剂（DES）为反应溶剂,原位添加铜盐催化剂,快速合成了纳米木质素基碳气凝胶前驱体（LRF）,经过高温一步热解处理得到木质素基碳气凝胶（LRFC）。研究结果表明,铜盐的原位掺杂加快了胶体形成的反应速率,缩短了LRF的成胶时间。其中,Cu（NO₃）₂的原位催化效果最好,可使得LRF凝胶点缩短至2.5 h;同时,其相应的碳气凝胶（N-LRFC）的微孔率高达94.44%,孔径集中分布在1 nm;在电流密度为0.5 A/g时,N-LRFC的比电容最高可达347.6 F/g,表现出优异的电化学性能,且在电化学过程中其扩散控制占主导地位。     

Study on the Pre-Treatment,Physical and Chemical Properties of Ramie Fibers Reinforced Poly (Lactic Acid) (PLA) Biocomposite

The comparative advantage of using vegetable fibers as reinforcement (fillers) attracted manufacturing industries over conventional composites. Natural fibers are purely green features that can easily decompose in a normal way to water and CO₂ when encountered with moisture during their disposal. In this research, the effect of pre-treatment and properties of ramie fibers reinforced polylactic acid (PLA) composite were studied. Before the composite preparation, ramie fibers were soaked in a solution of alkali (sodium hydroxide) and silane coupling agent to provide better compatibility between ramie fibers and PLA interface. Additionally, a design containing nine samples was conducted to study the effect of temperature, fiber volume ratio, molding pressure and time on composite fabrication. From the results, optimum processing parameters were identified based on the tensile, bending and impact strengths improvement from various tested samples. Furthermore, this study highlights the degradation process and properties of ramie fibers reinforced PLA composites by underground burial experimental procedures.     

L-半胱氨酸聚合膜亚硝酸盐安培传感器的制备及在食品检测中的应用

将L- 半胱氨酸通过循环伏安法电聚合到玻碳电极表面,制备了一种聚合物薄膜修饰电极,构建了一种新型NO2 安培传感器。实验结果表明,NO2 在该传感器上表现出良好的安培响应。其稳态电流与NO2 的浓度在1.0 × 10-6～4.4 × 10-5mol/L 范围内呈现良好的线性关系,检测限为1.0 × 10-7mol/L。此传感器具有灵敏度高、检测限低、抗干扰能力强等优点,应用于食品中NO2 含量的测量,结果满意。     

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.     

曲酸对动物的毒性研究及安全性评价

目的:研究曲酸对动物的毒性作用及安全性评价。方法:急性毒性实验、105d喂养实验。结果:曲酸对小鼠有明显的急性毒性作用,LD50为2571mg/kgbw,在105d大鼠喂养实验中,曲酸对大鼠生长发育、总食物利用率、血液生化指标、多个脏器的脏器系数,以及部分血液指标均无显著影响,但曲酸使雌、雄鼠白细胞数、淋巴细胞数明显下降,中性粒细胞数明显增加,各剂量组之间有剂量-效应关系,T3、T4有下降趋势,500mg/kgbw组少数动物出现了睪丸发育不良、甲状腺间质增生、肾脏和肝脏部分病理改变。结论:曲酸属低毒物质,长期高剂量使用可能会影响实验动物的生长发育及器官的结构和功能改变。     

Grafting of Poly(Methacrylic Acid) on Starch and Poly(Vinyl Alcohol)

Grafting of methacrylic acid (MAA) on starch, poly(vinyl alcohol) (PVA), and a mixture of starch and PVA, using a potassium persulfate/ sodium thiosulfate redox initiation system was carried out. Polymerization was studied with respect to graft yield, homopolymer formation and total conversion. These polymerization criteria were found to depend largely on the concentration of both MAA and initiators, duration and method of polymerization. The results reveal a number of interesting points which reflect the impact of the condition of the treatment. The main product of the polymerization reaction [poly(MAA)‐starch/PVA graft copolymer] was formed and precipitated during polymerization and can be easily separated by filtration as pure product. Application of these copolymers to cotton fabric was also carried out to evaluate the suitability of such modified products as sizing agents.