L-半胱氨酸自组装膜修饰电极对对氨基酚电催化氧化及其分析应用

在裸金电极上制备了L 半胱氨酸自组装膜修饰电极(L Cys/AuSAMs),研究了对氨基酚(p AP)在L Cys/AuSAMs上的电化学行为,发现该膜电极对p AP的氧化具有良好的电催化作用。氧化峰电位降低了128mV,测得p AP的扩散系数D为1.27×10-6cm2·s-1,初步探讨了电催化机理。采用水平衰减全反射 傅立叶变换红外光谱(ATR FTIR)技术对L Cys/AuSAMs进行了表征;方波伏安法(SquareWaveVoltammetry,SWV)测定p AP,其氧化峰峰电流与p AP浓度在1.0×10-8～8.0×10-8mol·L-1和1.0×10-7～2.0×10-4mol·L-1范围内呈线性关系,相关系数分别为0.9978和0.9977,检出限为2.0×10-9mol·L-1。该电极用于模拟废水样的测定,结果满意。     

L-半胱氨酸自组装膜修饰金电极对抗坏血酸的电催化作用及其测定

金电极表面对L 半胱氨酸 (L Cys)有特性吸附 ,而L Cys分子在等电点pH附近因静电引力和氢键作用形成分子对 ,从而在电极表面自组装形成L Cys双层膜。L Cys修饰金电极对抗坏血酸 (AA)具有良好的电催化作用。用示差脉冲伏安法对AA进行了测定 ,氧化电流与AA的浓度在 1.0× 10 -3 ～ 4× 10 -6mol/L范围内呈良好的线性关系 ,线性相关系数为 0 .9981;检出限为 4× 10 -7mol/L。用于药片中AA含量的测定 ,结果令人满意。     

L-半胱氨酸自组装膜修饰金电极的电化学特性

采用电化学石英晶体微天平（EQCM）和循环伏安法（CV）研究了L-半胱氨酸在金电极表面形成自组装膜的机理及其电化学性质.结果表明, L-半胱氨酸分子在金电极表面有特性吸附，而且在等电点pH附近因静电引力和氢键作用形成分子对，从而自组装形成双层膜.该膜电极在0.2 mol•L－1的醋酸缓冲溶液中，于－0.2～0.5 V(vs SCE)间CV扫描出现了一对稳定的氧化还原峰，并对抗坏血酸的氧化有良好的催化作用.     

铜卟啉-L-半胱氨酸自组装复合膜修饰电极的制备及电化学性能研究

利用电化学扫描法在L 半胱氨酸(Cys)自组装单分子膜修饰金电极表面现场制备了金属卟啉复合膜,对其进行SEM和ATR FTIR表征。修饰电极的支持电解质以及pH值对膜的稳定性和灵敏度有很大影响。铜卟啉 L Cys膜对H2O2具有良好的电催化还原特性,催化电流与H2O2浓度在1 0×10 6到3 0×10 5mol·L 1范围内线性关系,相关系数0 9995,检测限达1 0×10 7mol·L 1。     

桑色素在L-半胱氨酸自组装膜修饰金电极上的电化学行为研究

在0.1mol/L(pH=4.7)的HAc NaAc缓冲溶液中,用L 半胱氨酸自组装膜修饰金电极对桑色素的电化学行为进行了初步的研究,考察了修饰时间、富集时间、富集电位、扫描速度、表面活性剂、金属离子等因素对其电化学行为的影响。研究发现,桑色素在0.44V(vs.SCE)左右产生一不可逆的氧化峰。该氧化峰电流与桑色素浓度在5×10-6～2×10-4mol/L范围内呈线性关系(相关系数r=0.9989),检出限为2×10-6mol/L,这比用裸金电极测试降低一个数量级。同时发现,十六烷基三甲基溴化铵(CTAB)对氧化峰电流有一定的增敏作用。该峰且随Pb2+浓度增大而线性增高,因此可用于Pb2+的测定。     

细胞色素c在L-半胱氨酸自组装膜电极上的电化学行为

细胞色素c在L-半胱氨酸自组装膜电极上的电化学行为;细胞色素c; L-半胱氨酸; H2O2; 金电极     

二茂铁/L-半胱氨酸修饰电极的电化学行为及电催化性能

利用配对试剂将二茂铁酰胺键合在L-半胱氨酸自组装单层膜(SAM)表面, 制成稳定的二茂铁/L-半胱氨酸修饰电极, 该电极在pH 7.0的磷酸盐缓冲液中有一对很好的氧化还原峰. 运用循环伏安法和交流阻抗谱详细研究了修饰电极的电化学行为, 测得电子转移系数为0.66, 表观电极反应速率常数为6.86 s-1. 该修饰电极对肾上腺素有很好的催化作用, 峰电流与肾上腺素浓度在2.0×10-7～1.0×10-5 mol·dm-3范围内呈现良好的线性关系.     

L-半胱氨酸自组装修饰金电极-不可逆双安培测定阿魏酸

在裸金电极上制备了L-半胱氨酸自组装膜金修饰电极(L-Cys/SAM-Au/CME),将自组装膜修饰电极用于不可逆双安培体系,利用阿魏酸在L-Cys/SAM-Au/CME上的氧化和KMnO4在裸金电极上的还原,构建双安培检测新体系,建立了在外加电压为0V条件下,流动注射双安培法直接测定阿魏酸的新方法。在0.05mol/LH2SO4溶液中,该氧化峰峰电流与阿魏酸浓度在5.0×10-7~8.0×10-5mol/L范围内呈线性关系(r=0.9961,n=10),其线性回归方程为i(nA)=4.16×107C 50,在1.0×10-4~1.0×10-3mol/L范围内呈线性关系(r=0.9955,n=5),其线性回归方程为i(nA)=5.6×106C 300,检出限为1.2×10-7mol/L。连续测定2.0×10-5mol/L阿魏酸溶液25次,电流值RSD为1.20%,进样频率为80样/h。该方法具有较宽的线性范围、较高的选择性和灵敏度,样品处理方法简单快速,适于在线分析。对阿魏酸钠盐注射液中阿魏酸的测定结果满意。     

多巴胺在聚L-半胱氨酸/多壁碳纳米管修饰电极上的电化学行为及其伏安测定

多巴胺;L-半胱氨酸;多壁碳纳米管;修饰电极     

银微盘电极上L-半胱氨酸的伏安行为研究

银微盘电极上Ｌ－半胱氨酸的伏安行为研究方宾,方惠群,陈洪渊（南京大学化学系,南京,２１００９３）关键词银微盘电极,Ｌ－半胱氨酸,循环伏安法由碳纤维、金、铂、铱等材料制成微电极的研究国内、外报道甚多［１～５］,但以银为材料制成的电极在生化物质方面的研究...     

聚L-白氨酸修饰电极伏安法测定痕量多巴胺的研究

用循环伏安法制备了聚L-白氨酸修饰玻碳电极,研究了多巴胺在聚L-白氨酸修饰玻碳电极上的电化学行为,建立了循环伏安法测定痕量多巴胺的新方法。实验结果表明,在pH 6.0的磷酸盐缓冲溶液中,多巴胺在聚L-白氨酸修饰玻碳电极上产生一对灵敏的氧化还原峰,峰电位分别为Epa=0.281V,Epc=0.170 V(相对Ag/AgCl电极)。峰电流与多巴胺的浓度在5.0×10-8~5.0×10-4mol/L的范围内有线性关系,检出限为5.0×10-9mol/L。对1.0×10-5mol/L多巴胺溶液平行测定9次,其相对标准偏差为4.0%。已用于针剂中多巴胺的测定。     

多巴胺在DTNB自组装膜上的电催化研究

在金电极表面制备了DTNB(5,5′ Di thiobis(2 nitrobenzoicacid))自组装单分子层膜(DTNB/AuSAM)。多巴胺在DTNB自组装膜上有一对可逆性良好的氧化还原峰,其氧化峰电流与多巴胺的浓度在5.0×10-6mol/L～1.0×10-4mol/L的范围内呈线性关系,检出限为1.0×10-6mol/L。在pH3.5的缓冲溶液中,在DTNB自组装膜上多巴胺和抗坏血酸的电化学响应可以明显区分,氧化峰电位分离达276mV。可用于抗坏血酸存在下多巴胺的检测。测定了盐酸多巴胺注射液中多巴胺的含量,其平均回收率为104%。     

Renewable manganous hexacyanoferrate-modified graphite organosilicate composite electrode and its electrocatalytic oxidation of L-cysteine

Manganous hexacyanoferrate (MnHCF) supported on graphite powder was dispersed into methyltrimethoxysilane-derived gels to yield a conductive composite, which was used as electrode material to construct a renewable three-dimensional MnHCF-modifed electrode. MnHCF acts as a catalyst, graphite powder ensures conductivity by percolation, the silicate provides a rigid porous backbone, and the methyl groups endow hydrophobicity and thus limit the wetting section of the modified electrode. Cyclic voltammetry was exploited to investigate the dependence of electrochemical behavior on supporting electrolytes containing various cations. The chemically modified electrode can electrocatalytically oxidize L-cysteine, and exhibits a distinct advantage of polishing in the event of surface fouling, as well as simple preparation, good chemical and mechanical stability, and good repeatability of surface renewal. Electronic Publication     

Electroanalysis of dopamine at a gold electrode modified with N-acetylcysteine self-assembled monolayer

Voltammetric behavior of dopamine (DA) on a gold electrode modified with the self-assembled monolayer (SAM) of N-acetylcysteine has been investigated, and one pair of well-defined redox peaks of dopamine is obtained at the SAM modified gold electrode. The oxidation peak current increases linearly with the concentration of dopamine in the range of  mol l⁻¹. The detection limit is 8.0×10⁻⁷ mol l⁻¹. This method will be applicable to the determination of dopamine in injection of dopamine hydrochloride, and the good recovery of dopamine is obtained. Furthermore, The SAM modified gold electrode can resolve well the voltammetric responses of dopamine and ascorbic acid (AA), so it can also be applied to the determination of dopamine in the presence of ascorbic acid.     

Detection of dopamine using self-assembled diazoresin/single-walled carbon nanotube modified electrodes

Ultrathin films of diazoresin(DR)/single-walled carbon nanotube(SWNT) were fabricated on thioglycollic acid(TGA) decorated gold(Au) electrodes by the self-assembly method combined with the photocrosslinlcing technique.The electrochemical behavior of dopamine(DA) at the DR/SWNT modified electrodes was studied using the cyclic voltammetry(CV) and differential pulse voltammetry(DPV) methods.Under the optimal conditions,a linear CV response to DA concentration from 1 μmol/L to 40 μmol/L was observed,and the detection limit of DA was 2.1 ×10~(-3) μmol/L via the DPV method in the presence of 10 μmol/L of uric acid(UA) or 2.5 × 10~(-3) μmol/L via the DPV method in the presence of10 μmol/L of ascorbic acid(AA).Moreover,the modified electrodes exhibited good reproducibility and sensitivity,demonstrating its feasibility for analytical purposes.     

Determination of acetaminophen by square wave voltammetry at a gold electrode modified by 4-amino-2-mercaptopyrimidine self-assembled monolayers

A 4-Amino-2-mercaptopyrimidine self-assembled monolayer (AMP SAMs/Au) modified gold electrode was prepared. The electrochemical behavior of acetaminophen on the AMP SAMs/Au was studied in Britton-Robinson (BR) buffer solution. Compared to a bare gold electrode, the modified electrode exhibits a significant enhancement in the oxidation current response for acetaminophen. The modified electrode was used for the determination of acetaminophen by square wave voltammetry. The oxidation current increased linearly with the concentration of acetaminophen in the range of 2.0 × 10⁻⁶−4.0 × 10⁻³ M. The modified electrode made it possible to eliminate the interference of dopamine (DA), brucine, epinephrine (EP), and norepinephrine (NE). The practical analytical utility was illustrated by the determination of acetaminophen in a commercially available drug. The text was submitted by the authors in English.     

Electrochemical behavior of a covalently modified glassy carbon electrode with aspartic acid and its use for voltammetric differentiation of dopamine and ascorbic acid

Aspartic acid was covalently grafted on to a glassy carbon electrode (GCE) by amine cation radical formation in the electrooxidation of the amino-containing compound. X-ray photoelectron spectroscopic (XPS) measurement and cyclic voltammetric experiments proved the aspartic acid was immobilized as a monolayer on the GCE. Electron transfer to Fe(CN)₆^4– in solution of different pH was studied by cyclic voltammetry. Changes in solution pH resulted in the variation of the charge state of the terminal group; surface pK_a values were estimated on the basis of these results. Because of electrostatic interactions between the negatively charged groups on the electrode surface and dopamine (DA) and ascorbic acid (AA), the modified electrode was used for electrochemical differentiation between DA and AA. The peak current for DA at the modified electrode was greatly enhanced and that for AA was significantly reduced, which enabled determination of DA in the presence of AA. The differential pulse voltammetric (DPV) peak current was linearly dependent on DA concentration over the range 1.8×10^–6–4.6×10^–4 mol L^–1 with slope (nA mol^–1 L) and intercept (nA) of 47.6 and 49.2, respectively. The detection limit (3) was 1.2×10^–6 mol L^–1. The high selectivity and sensitivity for dopamine was attributed to charge discrimination and analyte accumulation. The modified electrode has been used for determination of DA in samples, in the presence of AA, with satisfactory results.     

Selective response of dopamine in the presence of ascorbic acid on L-cysteine self-assembled gold electrode

A L-cysteine (L-Cys) self-assembled modified gold electrode was used to detect dopamine (DA) by chronoamperometric method (CE) in the presence of ascorbic acid (AA). The defective limit is 2.0 x 10(-8) mol L(-1) (S/N=3). The proposed method was applied to detect DA in the samples with satisfied result.     

酞菁钴修饰碳糊电极对微量苯酚的测定

研究了苯酚在酞菁钴修饰碳糊电极上的电化学行为,提出了催化反应的机理,并以此为依据,用伏安法以酞菁钴修饰碳糊电极为工作电极测定了微量苯酚.在pH 8.7的磷酸盐缓冲溶液(PBS)中,苯酚在0.61 V(对SCE)出现一氧化峰,该峰电流与苯酚的浓度在5.0×10-7～1.0×10-4 mol/L之间呈线性关系,检出限为1.0×10-7 mol/L.此法可用于工业废水中苯酚的测定.     

Determination of nitrite with a nano-gold modified glassy carbon electrode by cyclic voltammetry

Abstract

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was employed to determine the concentration of rare earth elements (REEs) in plants and soils. Sample preparation and analytical conditions were investigated to set up a simple routine procedure for measuring rare earth elements. For prompt sample decomposition, a microwave digestion technique was successfully used with an acid mixture of HCl+HNO₃+HF. Detection limits, reproducibility, accuracy and possible interference were also studied. ICP-MS provided extremely low detection limits for REEs (0.6–6ng/l). Precision was typically better than 6% RSD (relative standard deviation) for soil and 10% for plant. The potential of the method was evaluated by analysis of standard reference materials of soils and plants. A good agreement between the experimental results and certified values was observed. The spectroscopic interference of Ba with Eu and light REEs(LREEs, La-Eu) with heavy REEs(HREEs, Gd-Lu) were eliminated by the algebra correction.

The results suggested that REEs in soil samples existed mainly as light REEs, and the same concentration distribution patterns of Oddo-Hakins law were observed, showing negative gradient from La to Lu concentrations. The REE contents in plants were very low, less than 20μg/g and varied with plant species. Apart from rape leaf(Brassica juncea), the REE distribution patterns in other plant leaves were consistent with soils, indicating that these plants generally absorbed REEs from soil without selectivity. Rape leaf showed selective absorption for LREEs, especially for La. The REE concentration distribution in parts of hot pepper(Capsicum annuum) was characteriaed by root>leaf>stem>fruit. The REEs absorbed by hot pepper concentrated mainly in roots and leaves, very little migrated into fruit. Transfer factors(TFs) of REEs in plants were very low. Although the contents of LREEs were relatively more than those of HREEs, no distinct difference of TFs between LREEs and HREEs was observed, meaning that LREEs and HREEs have the same abilities of transportation. However, for rape leaf, the TFs of LREEs were one or two orders of magnitude higher than those of HREEs.