氨基酸席夫碱双核铜配合物修饰玻碳电极对抗坏血酸的电催化作用

采用电沉积方法将丝氨酸席夫碱双核铜配合物修饰于玻碳(GC)电极表面制得了修饰电极.研究了[Cu_2L_2(4,4′-Bipy)]/GC电极的电化学性质, 并发现该电极对抗坏血酸(AA)具有良好的电催化氧化作用.考察了该电极作为AA传感器的操作条件, 结果表明: 修饰电极在pH=7.0的磷酸盐缓冲溶液(PBS)中,于-0.70～0.10 V的范围内,以50 mV·s~(-1)的扫描速率进行循环伏安扫描, 催化电流峰与AA浓度在0.2×10~(-4)～1.0×10~(-4)mol·L~(-1)范围内呈线性关系.这表明可利用该修饰电极对抗坏血酸作定量分析.对2种水果汁饮料中AA进行测定, 其果汁含量分别为0.0647 g·L~(-1)和0.125 g·L~(-1),相对标准偏差在2.4%～3.0%之间.     

聚对苯二酚修饰玻碳电极的制备及其对抗坏血酸的催化氧化作用

采用循环伏安(CV)法制备了聚对苯二酚薄膜修饰玻碳电极,利用其电催化氧化作用建立了抗坏血酸的定量分析方法,探讨了其催化氧化机理。研究发现:在0.2 mol/L Na2HPO4-NaH2PO4(PBS,pH 7.0)缓冲溶液中,以0.1 mol/L KC l作支持电解质,聚对苯二酚修饰电极(PHQ/CME)对抗坏血酸(AA)存在灵敏的催化氧化作用,氧化峰电位负移177 mV。应用微分脉冲伏安法(DPV)对AA进行定量分析,其氧化峰电流与AA浓度在3.3×10-5~1.7×10-2mol/L和1.7×10-2~1.2×10-1mol/L范围内呈良好的线性关系,检出限为3.3×10-6mol/L。机理研究结果表明:PHQ/CME上带有的酚羟基与脱氢抗坏血酸自由基之间形成的氢键是电催化氧化的主要原因。     

抗坏血酸在PPy-HEImTfa/Pt电极上的电催化氧化及其机理

以铂为基底电极,在1-乙基咪唑三氟乙酸盐(HEImTfa)离子液体中电化学合成导电聚吡咯(PPy),制得PPy-HEImTfa/Pt电极;采用循环伏安法研究了PPy-HEImTfa/Pt电极对抗坏血酸的电催化氧化性能.结果表明:PPy-HEImTfa/Pt电极对0.1mo·lL-1抗坏血酸具有较高的电催化氧化活性,与相同条件下硫酸溶液中在铂表面修饰的聚吡咯(PPy-H2SO4/Pt)电极和裸铂电极相比,其氧化峰电位分别降低了0.10和0.19V,氧化峰电流分别增加了3.0和3.6mA.同时采用原位傅里叶变换红外(insitu FTIR)光谱技术对抗坏血酸在PPy-HEImTfa/Pt电极上的电氧化机理进行了研究,结果表明:抗坏血酸在PPy-HEImTfa/Pt电极上首先被氧化为脱氢抗坏血酸,在水溶液中脱氢抗坏血酸迅速发生水合作用形成水合脱氢抗坏血酸,它进一步水解并发生内酯开环反应生成2,3-二酮古洛糖酸;在较高电位下,部分抗坏血酸最终被氧化成CO2.     

银掺杂聚谷氨酸修饰电极对抗坏血酸的催化氧化

通过循环伏安法(CV)制备了银掺杂聚谷氨酸修饰玻碳电极(Ag/PGA/GCE),研究了抗坏血酸(AA)在该修饰电极上的电化学行为。结果表明:Ag/PGA/GCE对AA的氧化具有良好的电催化活性,可显著降低AA的氧化电位,同时增强AA的氧化峰电流。利用该修饰电极成功检测了药片中的AA含量。     

电化学方法制备石墨烯-铁氰化镍复合物及对抗坏血酸的电催化氧化研究

采用电化学还原方法制备了铁氰化镍-石墨烯复合薄膜电极,扫描电子显微镜(SEM)表征电还原石墨烯和铁氰化镍-石墨烯复合材料的表面形貌。采用循环伏安和计时电流技术研究了该修饰电极对抗坏血酸(AA)的电催化氧化性能,据此建立了一种测定AA的电化学分析新方法。由于石墨烯和铁氰化镍纳米颗粒之间的协同效应,使得该复合修饰电极对抗坏血酸具有优异的电催化活性。在0.1 mol/L pH 7.00的PBS溶液中,抗坏血酸的催化氧化电流与其浓度在1.0×10-4~7.0×10-4mol/L范围内呈良好的线性关系,检出限为3.1×10-5mol/L(S/N)。     

PmClAn基膜修饰电极的电化学及催化性质研究

聚苯胺作为电极修饰材料 ,已在传感器上显示出广泛的应用前景[1～ 4 ] .异丙醇 ( i- P)氧化[5,6 ] 是个较简单的反应 ,被广泛作为电催化研究的模型反应 .目前 ,i- P电化学氧化的研究集中于 Pt的多晶或单晶电极[7～ 9] ,Gonzales等 [10 ] 报道了 Pt- Sn共沉积的 PAn膜修饰电极上的异丙醇电氧化 ,但对复合材料的微观结构仍欠研究 .本文讨论 Pm Cl An基质性质对 Pt电沉积的影响 ,并探讨了 i- P在沉积 Pt微粒的 Pm Cl An功能膜电极上的氧化情况 .1　实验部分1 .1　电极的制备　聚间氯苯胺 ( Pm Cl An,本征态 ud,HCl掺杂态 d)采用乳液聚…     

高选择性的镍基无酶葡萄糖微传感器的研制及应用

采用电刻蚀法制得微镍电极,通过循环伏安法在微镍电极上修饰过氧化聚吡咯膜,利用葡萄糖在碱性条件下在该修饰电极上的电催化氧化性质,制备了新型的抗干扰的无酶葡萄糖微传感器;研究了其电化学氧化机理,在较低的碱性(pH=12.0)和较低的氧化电位( 0.47 V)条件下,微镍修饰电极上产生的Ni(Ⅲ)能直接将葡萄糖氧化为葡萄糖酸内酯,产生的安培响应与葡萄糖浓度在5.0×10-6 ～1.1×10-3 mol/L范围内呈线性关系;检出限为2.4×10-6 mol/L.该微传感器灵敏度高(30.4 nA/μM)、选择性好(20倍AA和UA不干扰)、响应快(小于3 s)、重现性好,而且制作简单、使用方便,已用于流动注射分析(FIA)测定血清中血糖含量.     

α-环糊精包结碳纳米管涂层电极同时测定多巴胺和肾上腺素

本文发现α-环糊精包结碳纳米管涂层电极对多巴胺（DA）和肾上腺素（EP）具有显著的增敏和电分离作用，还原峰电位差达390 mV。研究表明α-环糊精包结碳纳米管涂层薄膜表现出了非常令人感兴趣的电催化特性。因抗坏血酸（AA）在α-环糊精包结碳纳米管涂层电极上的氧化是不可逆的，因此利用还原峰进行测定，消除了AA对DA和EP的干扰。由于成本低和制作简便，该电极可用于生物系统电化学研究的生物传感器。     

聚中性红/纳米二氧化硅复合修饰电极直接测定抗坏血酸

用滴涂法和电化学聚合法制备了聚中性红/纳米二氧化硅修饰电极(PNR/nano-SiO2/GCE),并用循环伏安法和交流阻抗法研究了修饰电极表面的电化学行为。实验表明,该修饰电极对抗坏血酸(AA)表现出良好的电催化氧化性能,探讨了复合修饰电极协同增效作用的机理。用线性扫描伏安法研究了AA浓度与峰电流之间线性关系,在pH2.0的磷酸盐缓冲溶液中,AA氧化峰电流在1.8×10-6～5.0×10-3mol/L浓度范围内呈良好的线性关系,检出限为5.4×10-7mol/L(S/N=3)。该修饰电极制备简单,可用于药品及果蔬食品中抗坏血酸的直接测定。     

新型双核铜配合物修饰玻碳电极对抗坏血酸的电催化作用及其测定

采用电沉积方法将双核铜配合物修饰于玻碳(GC)电极表面制得了[LCu]2biPy/GC电极。研究了[LCu]2biPy/GC电极的电化学性质,并发现该电极对抗坏血酸具有良好的电催化氧化作用。考察了该电极作为抗坏血酸传感器的操作条件,结果表明:修饰电极在pH 7.0的磷酸盐(PBS)缓冲溶液,-0.2~0.8 V电位范围内,以50 mV.s-1进行循环伏安扫描,催化电流峰与抗坏血酸浓度在4.0×10-5~1.2×10-4mol.L-1范围内呈线性关系,检出限为2.5×10-6mol.L-1。用于3种水果汁中抗坏血酸的测定,测定结果的RSD在1.6%~2.1%之间,回收率在97.8%~102.1%之间。     

聚色氨酸／镍复合膜修饰电极测定抗坏血酸的研究

采用电化学聚合法制备了聚色氨酸／镍复合膜修饰玻碳电极,研究了抗坏血酸在该修饰电极上的电化学行为,建立了测定痕量抗坏血酸的新方法。在pH6．2的磷酸盐缓冲溶液中,抗坏血酸在修饰电极上产生一个灵敏的氧化峰,采用线性扫描伏安法测定,其氧化峰电流与抗坏血酸浓度在2．0×10^-6 -1．0×10^-3mol／L范围内呈良好的线性关系,检出限为5．0×10^-7mol／L。对1．0×10^-4mol／L抗坏血酸溶液平行测定6次,测定结果的相对标准偏差为1．9％。该法用于片剂中抗坏血酸含量的测定,加标回收率为97．8％～101．2％。     

苯胺在邻-氨基苯磺酸功能化的玻碳电极上聚合及其对抗坏血酸的电催化氧化

通过电氧化法将ABS分子以CN键共价键合在玻碳电极(GCE)表面,形成ABS分子单层膜修饰的GCE(ABS/GCE),在此电极上对AN进行电聚合,从而制备了聚苯胺/邻氨基苯磺酸复合膜修饰电极(PAN-ABS/GCE/CME).由于ABS中磺酸基功能团对PAN的掺杂作用使PAN在中性或碱性介质中都能呈现出较好的电化学活性.研究表明,PAN-ABS/GCE/CME在PBS(pH 6.8)中对AA的电氧化具有催化作用,其氧化峰电位为0.17 V,比在裸GCE上(0.39 V)负移了0.22 V,峰电流明显升高.AA在修饰电极上的氧化峰电流与其浓度在0.5～16.5 mmol/L范围内呈良好的线性关系,其线性回归方程为ipa(μA)=20.2+6.20CAA,r=0.9973; 检出限(3δ)为7.2 μmol/L,电极具有较好的稳定性和重现性.并采用计时电流法对AA催化氧化的扩散系数和催化速率常数进行了研究.     

Synthesis of Pt/ionic liquid/graphene nanocomposite and its simultaneous determination of ascorbic acid and dopamine

A water-soluble and electroactive composite - Pt nanoparticles/polyelectrolyte-functionalized ionic liquid (PFIL)/graphene sheets (GS) nanocomposite was synthesized in one pot. The structure and composition of the Pt/PFIL/GS nanocomposite were studied by means of ultraviolet-visible (UV-vis) and X-ray photoelectron spectra (XPS). Scanning electron microscopy (SEM) and transmission electron microscope (TEM) images reveal Pt nanoparticles are densely dispersed on the transparent thin PFIL-functionalized graphene sheets. The obtained Pt/PFIL/GS nanocomposite-modified electrode was fabricated to simultaneously determine ascorbic acid (AA) and dopamine (DA) by cyclic voltammetry. It is worthwhile noting that the difference between the two peak potentials of AA and DA oxidation is over 200 mV, which leads to distinguishing AA from DA. The detection of increasing concentrations of AA in the presence of DA and the oxidation of continuous addition of DA in the presence of AA were also studied using differential pulse voltammetry. The proposed sensor in real sample analysis was also examined in human urine samples. Three independent oxidation peaks appear in urine sample containing AA and DA. Therefore, the Pt/PFIL/GS nanocomposite might offer a good possibility for applying it to routine analysis of AA and DA in clinical use.     

聚茜素红膜修饰电极控制电位扫描法分别测定多巴胺和抗坏血酸

研究了聚茜素红膜修饰电极(PARE)的制备及其对多巴胺(DA)和抗坏血酸(AA)的电催化性能,结果表明,在PARE上DA和AA具有不同的循环伏安行为,前者表现为一个准可逆过程,后者则为不可逆过程,并且二者的氧化峰电位分开近200mV.因此可通过控制不同的电位范围进行分步扫描,实现了对同一体系中DA和AA的分别测定,DA的还原峰电流和AA的氧化峰电流分别在8.0×10^-6～4.0×10^-3mol/L和4.0×10^-5～2.0×10^-2mol/L范围内与各自的浓度呈线性关系;检测限分别为8.0×10^-7mol/L和1.0×10^-5mol/L.同时与导数伏安法一步测定进行比较,结果令人满意.     

Electrochemical determination of vitamin C in the presence of uric acid by a novel TiO2 nanoparticles modified carbon paste electrode

<正>The electrochemical behavior of vitamin C(ascorbic acid or AA) is investigated on the surface of a carbon-paste electrode modified with TiO_2 nanoparticles and 2,2'-(1,2 butanediylbis(nitriloethylidyne))-bis-hydroquinone(BBNBH).The prepared modified electrode showed an efficient catalytic role in the electrochemical oxidation of AA,leading to remarkable decrease in oxidation overpotential and enhancement of the kinetics of the electrode reaction.This modified electrode exhibits well-separated oxidation peaks for AA and uric acid(UA).The modified electrode is successfully applied for the accurate determination of AA in pharmaceutical preparations.     

Determination of ascorbic acid in pharmaceutical dosage forms and urine by means of an oscillatory reaction system using the pulse perturbation technique

A simple and reliable method for the determination of ascorbic acid (AA) is proposed and validated. It is based on potentiometric monitoring of the concentration perturbations of an oscillatory reaction system in a stable nonequilibrium stationary state close to the bifurcation point. The response of the Bray–Liebhafsky (BL) oscillatory reaction as a matrix, to the perturbation by different concentrations of AA, is followed by a Pt electrode. The linear relationship between maximal potential shift and the logarithm of the amount of AA is obtained between 0.01 and 1.0 μmol. The sensitivity of the proposed method (as the limit of detection) is 0.009 μmol and the method has excellent sample throughput (30 samples per hour). The procedure was used for AA determination in pharmaceutical formulations and urine. The results are in agreement with those obtained using the official method. Some aspects of the possible mechanism of AA action on the BL oscillating chemical system are discussed.     

The Influencing Mechanism of Acidity on the Oxidation Peak Currents of Uric Acid and Ascorbic Acid at the PACPE by Cyclic Voltammetry

In this paper, a pre‐anodized carbon paste electrode (PACPE) is fabricated by a simple electrochemical pretreatment method, which can be used for the simultaneous determination of uric acid (UA) and ascorbic acid (AA). The influencing mechanism of the acidity on the size of oxidation peak current (i_p,a) of UA and AA is discussed in detail. According to the results, in different pH conditions, the intensity of hydrogen bonding between UA, AA and the surface of PACPE, the degree of reduction reaction at the auxiliary electrode, and the structural configurations of UA and AA with different species in reaction system have evident influence on the size of oxidation peak current. In pH 7.00 phosphate buffer solution, the calibration curves for UA and AA are obtained in the range of 5.0 x 10^‐7–5.0 x 10^‐5 mol/L and 3.0 x 10^‐5–5.0 x 10^‐3 mol/L, respectively. The detection limits for UA and AA are found to be 2.0 x 10^‐8 mol/L and 1.2 x 10^‐6 mol/L, respectively. This proposed method has been successfully applied to determine UA and AA in human urine simultaneously with satisfactory results.     

肉桂酸修饰电极同时测定多巴胺和抗坏血酸的研究

用电化学聚合方法制备肉桂酸(CA)修饰的玻碳电极(PCA/GC),研究多巴胺(DA)和抗坏血酸(AA)在修饰电极上的电化学行为.结果表明,在DA和AA共存体系中,DA、AA在PCA/GC电极上氧化峰电流增大且氧化峰电位相差200 mV,据此可同时检测DA和AA.在pH 7.0磷酸盐缓冲液中,DA和AA的氧化峰电流与其浓...     

Selective Voltammetric Detection of Uric Acid in the Presence of Ascorbic Acid at Well‐Aligned Carbon Nanotube Electrode

The voltammetric behaviors of uric acid (UA) and L ‐ascorbic acid (L ‐AA) were studied at well‐aligned carbon nanotube electrode. Compared to glassy carbon, carbon nanotube electrode catalyzes oxidation of UA and L ‐AA, reducing the overpotentials by about 0.028 V and 0.416 V, respectively. Based on its differential catalytic function toward the oxidation of UA and L ‐AA, the carbon nanotube electrode resolved the overlapping voltammetric response of UA and L ‐AA into two well‐defined voltammetric peaks in applying both cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which can be used for a selective determination of UA in the presence of L ‐AA. The peak current obtained from DPV was linearly dependent on the UA concentration in the range of 0.2 μM to 80 μM with a correlation coefficient of 0.997. The detection limit (3δ) for UA was found to be 0.1 μM. Finally, the carbon nanotube electrode was successfully demonstrated as a electrochemical sensor to the determination of UA in human urine samples by simple dilution without further pretreatment.