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。     

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.     

丝素蛋白负电性增强改性及其对降钙素基因相关肽的加载能力

为提高丝素蛋白(SF)材料的快速内皮化能力,解决血管组织工程面临的血栓和内膜增生难题,将具有双向调控血管细胞生长功能的降钙素基因相关肽(CGRP)通过静电相互作用引入丝素蛋白材料表面。首先选用含有2个羧基的己二酸(AA)与丝素蛋白分子进行反应,采用流延法制备AA改性SF膜,研究了改性SF膜的结构和膜表面对CGRP分子的加载能力。结果表明:随着AA质量占比的增加,SF的Zeta电位逐渐减小,当SF与AA的质量比由100:0变化为100:2.5时,SF的Zeta电位由-2.66 mV 下降至-5.4 mV;AA改性SF材料中引入了新的羧基和酰胺键,形成了以β-折叠结构为主的分子构象和Silk Ⅱ结晶结构;当SF与AA的质量比为100:2.5时,AA改性SF膜表面静电作用加载的CGRP含量比未改性SF膜提高了9倍。     

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.     

微波消解-铋膜/Nafion修饰电极溶出伏安法测定鳗鱼中的镉含量

运用铋膜/Nafion修饰电极耦合微波消解技术测定鳗鱼中的Cd2+。Cd2+在－0.85V处出现清晰的方波氧化峰。Nafion、铋膜的厚度、缓冲液的pH值、富集电位、富集时间及可能干扰物质的影响因素进行考察。Cd2+在4.0～14.0μg/L质量浓度范围内线性关系,线性相关性系数为0.9964,检出限为0.2μg/L。结果表明,该传感器在过量的干扰离子存在条件下,表现出超灵敏性和有效性。     

改性羰基铁粉制备及其在蓝光固化磁控超疏水薄膜中的应用

针对超疏水涂层膜在固化过程中功能性颗粒的不受控运动以及传统的热固化能耗高、耗时长的缺点,通过对羰基铁粉进行改性,并将磁控技术和蓝光固化技术相结合构筑超疏水薄膜。分析改性剂质量比、用量、pH值以及温度对羰基铁粉改性效果的影响,确定最佳改性工艺;研究了磁场强度对光固化薄膜表面接触角以及形貌的影响规律。结果表明:当改性剂3-(甲基丙烯酰氧)丙基三甲氧基硅烷与1H,1H,2H,2H-全氟葵基三甲氧基硅烷质量比为1:3,质量分数为20%,pH值为6,温度为75 ℃,时间为1.5 h时,羰基铁粉表面改性效果最佳,其活化度达到96%,Zeta电位绝对值由22 mV提高至43 mV;随着磁感应强度的增加,薄膜表面接触角不断增加,当磁感应强度为75 mT时,超疏水薄膜的表面接触角达到157.6°,滚动角为6°,符合超疏水标准。     

家蚕丝素蛋白阳离子化及其对羊毛性状的影响

为提高羊毛织物的穿着舒适性,以碳化二亚胺(EDC)为激活剂激活家蚕丝素蛋白侧链上的羧基,使其与精胺反应得到阳离子化丝素蛋白,并将其整理到羊毛上,借助扫描电子显微镜、X射线衍射仪、傅里叶红外光谱仪、差示扫描热量仪对整理后的羊毛进行分析与表征。结果表明:整理后的丝素蛋白Zeta电位由-3.58 mV上升到5.41 mV;改性羊毛鳞片层表面被丝素蛋白膜包裹,其表面形成了更多的氢键和酰胺键,晶体结构更稳定,耐热分解性能提高,但力学性能下降;不同改性程度的家蚕丝素蛋白对羊毛结构的影响无明显差异,改性处理使羊毛酸性染料上染率下降。     

聚苯胺修饰钨丝针型复合微PH传感器的研究及在水果测试中的应用

由电聚合法将聚苯胺修饰的钨丝电极作为ｐＨ敏感电极,把Ａｇ－ＡｇＣｌ体系填入针型塑料管内构成参比电极,把经聚苯胺修饰的钨丝电极安置入该针型参比电极内构成复合针型微ｐＨ传感器,在ｐＨ２￣１２范围内,该传感器呈现Ｎｅｒｎｓｔ响应,斜率为５５ｍＶ／ｐｈ,响应时间〈１ｍｉｎ,该传感器成功地应用于水果内微区ｐＨ的测定。     

New voltammetric procedure for determination of thiamine in commercially available juices and pharmaceutical formulation using a lead film electrode

A simple, reliable and reproducible method, based on adsorptive stripping voltammetry (AdSV), for determination of vitamin B₁ (thiamine) in pharmaceutical preparation and food is described in this paper. The in situ plated lead film electrode was used as a working electrode. The lead film was formed and thiamine was accumulated at −1.25 V (vs. Ag/AgCl) on a glassy carbon electrode. Then, the preconcentrated thiamine was reduced by scanning the potential of the electrode from −1.25 to −1.55 V using a square-wave technique. The linear range was from 0.0133 to 0.265 mg L⁻¹ for vitamin B₁, with the regression coefficient of 0.999. The detection limit for vitamin B₁ was 0.0053 mg L⁻¹ for the accumulation time 120 s. The method developed was applied to the determination of thiamine in certified reference material (BCR-485), pharmaceutical formulation and commercially available juices, and the assay results were satisfactory.     

抗坏血酸在聚对苯二酚/铜复合膜修饰电极上电催化氧化行为的探究

利用电沉积法制备了聚对苯二酚/铜(PHQ/Cu)复合膜修饰电极,并采用循坏伏安法探究了抗坏血酸(AA)在该电极上的电催化氧化行为。结果表明,与裸电极、PHQ修饰电极相比,PHQ/Cu复合膜修饰电极对AA具有更好的催化作用,表明两种修饰剂对AA的电催化氧化有良好的协同催化作用;在0.1 mol/L磷酸盐缓冲溶液(pH=4.35)中,AA的氧化峰电流与其浓度在5×10-4~1.0×10-1 mol/L范围内呈良好的线性关系,线性方程为lgI=0.7364lgc+1.6932,R2=0.9959,检出限为2.0×10-5 mol/L。该复合膜修饰电极在冰箱内贮存9 h,其电化学信号基本保持不变,且共存物几乎不干扰AA的测定,表明电极具有良好的稳定性和较强的抗干扰能力,可以用于饮料中AA含量的测定,回收率在95.5%~109.1%之间。     

A novel nanosensor based on Pt:Co nanoalloy ionic liquid carbon paste electrode for voltammetric determination of vitamin B9 in food samples

In this work we describe a novel nanoalloy (Pt:Co) room temperature ionic liquid (RTIL) modified carbon paste electrode as a high sensitive sensor for voltammetric determination of vitamin B₉ in food samples. The sensor exhibits an enhanced effectiveness for the electro-oxidation of vitamin B₉ in aqueous solution. The oxidation peak potential for this matter at a surface of the ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate) Pt:Co carbon paste electrode (Pt:Co/IL/CPE) appeared at 685 mV that was about 110 mV lower than the oxidation peak potential at the surface of the traditional carbon paste electrode (CPE) under similar condition. The mechanism of the electro-oxidation process on the surface of the modified electrode was analyzed. Square wave voltammetry (SWV) was applied as a very sensitive electrochemical method for the determination of sub-micro-molar amounts of vitamin B₉. The linear response range and detection limit were found to be 1.0 × 10⁻⁷ to 5.0 × 10⁻⁴ M and 4.0 × 10⁻⁸ M, respectively. The prepared modified electrode shows several advantages such as simple preparation method, high stability, high sensitivity, and excellent catalytic activity, long-term stability and remarkable voltammetric reproducibility for eletrooxidation of vitamin B₉. The proposed sensor was successfully applied for the determination of vitamin B₉ in food samples.     

聚嘧啶/石墨烯复合材料修饰电极同时测定日落黄和酒石黄

采用液相剥离法制备石墨烯纳米片悬浮液,将其直接滴涂于玻碳电极表面,制备石墨烯修饰电极,再采用电沉积法制得聚嘧啶/石墨烯复合膜修饰电极。采用扫描电子显微镜对该修饰电极的表面形貌进行表征;采用循环伏安法和方波伏安法探究日落黄和酒石黄在该修饰电极上的电化学行为。结果表明,该复合膜修饰电极对两种合成色素均表现出良好的电催化性能。在优化实验条件下,日落黄和酒石黄同时被检测,线性检测范围分别为0.002~2?mol/L和0.003~6?mol/L,检测限分别为0.5 nmol/L和0.9 nmol/L。该方法可用于食品中日落黄和酒石黄的同时测定。     

微波消解-Nafion修饰电极溶出伏安法测定海带中的铅含量

建立一种基于微波消解-Nafion修饰电极溶出伏安法用于检测海带中的铅离子。铅离子在－0.62V处出现了清晰的氧化峰。对Nafion的浓度、缓冲液的pH值、富集电位、富集时间及可能存在的干扰物质进行考察。铅离子在6.0～16.0μg/L范围内呈线性关系,线性相关性系数为0.9984,检出限为0.04μg/L。结果表明,该传感器在过量的干扰离子存在条件下,表现出超灵敏性和有效性。     

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。     

基于方波伏安法的聚多巴胺@纳米银修饰玻碳电极测定畜禽肉中氯丙嗪

基于多巴胺(dopamine,DA)的自聚反应,在纳米银(sliver nanoparticles,AgNPs)和玻碳电极(glassy carbon electrode,GCE)表面形成聚多巴胺(polydopamine,PDA)膜,使AgNPs均匀分散在GCE表面,得到PDA@AgNPs/GCE修饰电极;对DA的自聚时间、氯丙嗪的电化学测试方法及条件等进行考察和优化,构建基于方波伏安法的氯丙嗪快速检测方法;利用循环伏安法、交流阻抗法和扫描电子显微镜对修饰电极进行表征。最佳条件下,氯丙嗪在PDA@AgNPs/GCE上的氧化峰电流与其浓度在5.0×10^-8～1.0×10^-5 mol/L范围内呈良好的线性关系(R²=0.991),检出限(R_SN=3)为1.7×10^-8 mol/L。用该法测定猪肉、鸡肉和牛肉中氯丙嗪的加标回收率分别为84.9%～88.8%、79.8%～93.8%、80.6%～93.9%。该方法所用测试仪器轻巧便携,修饰电极的制备方法简便易行、成本低、便于批量制备,...     

油酸和亚油酸在聚吡咯修饰铂电极上的电化学反应

基于醌的电化学还原原理,利用1,4-萘醌对游离脂肪酸的还原峰电流的测定,检测植物油中油酸和亚油酸的浓度,从而求出所测植物油的酸价。采用循环伏安法在乙腈溶液中聚合吡咯单体于铂电极表面制备化学修饰电极Ppy/ClO4-/Pt,用线性伏安法检测油酸和亚油酸浓度。结果表明:在浓度分别为5.3×10-3～7.9×10-2mol/L和9.6×10-6～1.28×10-3mol/L之间,还原峰电流与油酸和亚油酸浓度呈现良好的线性关系,相关系数(R2)分别是0.9948和0.9922,亚油酸和油酸的检出限为3.0×10-6mol/L和1.6×10-3mol/L(S/N=3)。并且将该化学修饰电极用于植物油橄榄油、玉米油、花生油、大豆油和芝麻油中酸价的检测,结果表明,化学修饰电极法是一种简便、快速实用的酸价滴定方法,可以作为碱滴定法的替代方法。     

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。     

电分析法测定植物油中抗氧化剂研究

主要研究抗氧化剂TBHQ、BHA和BHT在玻碳电极上伏安性质,三者循环伏安图表明,三个峰形良好氧化峰分别对应:TBHQ氧化峰电位为590mV,BHA氧化峰电位为710mV,BHT氧化峰电位为1050mV,只有一个还原峰,电位为-90mV。通过试验优化电分析法测定植物油样抗氧化剂分析技术参数;借助最小偏二乘法(PLS),利用电分析法预测人工模拟试样中三种抗氧化剂含量,结果令人满意。该研究利用所开发方法测定实际油样中抗氧化剂含量,其回收率为94～104.1%;结果表明,该法同时测定植物油中两种及以上抗氧化剂是可行的,且无需提取、分离及清洗等预处理程序,应用潜力巨大。     

差分脉冲伏安法对果蔬中亚硝酸盐和抗坏血酸的同时测定

采用对苯二酚（Hydroquinone，HQ）催化甲烷氧化菌素（Methanobactin，Mb）还原氯金酸合成纳米金（Gold Nanoparticles，AuNPs），利用电沉积法将Mb@AuNPs修饰到裸金电极表面，制备Mb@AuNPs/Au电极。采用差分脉冲伏安法对亚硝酸盐和抗坏血酸进行同时测定并对条件进行优化，结果表明:电极组装条件为电沉积扫速100 mV/s、扫描圈数为40圈；检测体系为浓度0.20 mol/L pH6.5的磷酸盐缓冲溶液，在2~5600 μmol/L和1~6000 μmol/L的线性范围内，Mb@AuNPs/Au对亚硝酸盐和抗坏血酸同时检测的氧化峰电流与浓度呈良好的线性关系（R2>0.9928），检出限分别为0.31和0.57 μmol/L。实际样品中亚硝酸盐和抗坏血酸的加标回收率范围分别为92.59%~109.26%、90.01%~103.51%，表明该方法具有良好的重现性和稳定性，可用于果蔬中亚硝酸盐和抗坏血酸的同时测定。     

Redox and pH microenvironments within Shewanella oneidensis MR-1 biofilms reveal an electron transfer mechanism

The goal of this research was to quantify the variations in redox potential and pH in Shewanella oneidensis MR-1 biofilms respiring on electrodes. We grew S. oneidensis MR-1 on a graphite electrode, which was used to accept electrons for microbial respiration. We modified well-known redox and pH microelectrodes with a built-in reference electrode so that they could operate near polarized surfaces and quantified the redox potential and pH profiles in these biofilms. In addition, we used a ferri-/ferrocyanide redox system in which electrons were only transferred by mediated electron transfer to explain the observed redox potential profiles in biofilms. We found that regardless of the polarization potential of the biofilm electrode, the redox potential decreased toward the bottom of the biofilm. In a fully redox-mediated control system (ferri-/ferrocyanide redox system), the redox potential increased toward the bottom when the electrode was the electron acceptor. The opposite behavior of redox profiles in biofilms and the redox-controlled system is explained by S. oneidensis MR-1 biofilms not being redox-controlled when they respire on electrodes. The lack of a significant variation in pH implies that there is no proton transfer limitation in S. oneidensis MR-1 biofilms and that redox potential profiles are not caused by pH.