黄嘌呤和尿酸在修饰电极上的电化学行为及测定研究

用循环伏安法制备了银掺杂聚L-赖氨酸修饰玻碳电极,并对修饰电极表面进行了表征,研究了黄嘌呤和尿酸在该修饰电极上的电化学行为,建立了循环伏安法和示差脉冲伏安法同时测定黄嘌呤和尿酸的新方法。研究表明,修饰电极对尿酸和黄嘌呤的氧化具有较好的电催化活性,在pH 3.0磷酸盐缓冲溶液中,黄嘌呤和尿酸在银掺杂聚L-赖氨酸修饰电极上的氧化峰电位分别为0.980和0.600 V,两者的峰电位差达0.380 V。在最优实验条件下,用差分脉冲伏安法同时测定黄嘌呤和尿酸的线性范围为1.0×10-6~2.5×10-4mol/L,检出限为5.0×10-7mol/L。用于人尿样中黄嘌呤和尿酸的测定,获得满意结果。     

银掺杂聚L-半胱氨酸修饰电极测定尿酸

尿酸(UA)是人体内嘌呤代谢最终产物,它在人体体内含量的变化可直接导致某些疾病的发生.因此,对尿酸的化学检测、尤其是人体体液中的含量测定,在临床医学中具有较大的现实意义.     

高效液相色谱测定人体液和组织中的尿酸、黄嘌呤和次黄嘌呤

尿酸、次黄嘌呤和黄嘌呤广泛分布于生物体内,它们是形成超氧自由基(O_2~-)的酶促反应底物。     

基于硫堇-碳纳米管修饰电极对过氧化氢的催化还原低电位检测尿酸

尿酸是人体内嘌呤代谢的最终产物.人体内尿酸浓度的改变会引起痛风、关节炎、肾病、神经系统疾病等.因此检测人体内尿酸的含量对于诊断和治疗这些疾病有着重要的意义~([1]).尿酸酶,葡萄糖,抗坏血酸,尿酸,4-对乙酰氨基酚,3,4-二羟基苯乙酸,十二烷基苯磺酸钠,硫堇,单壁碳纳米管,过氧化氢,0.1 mol/L PBS缓冲溶液.     

电化学预处理玻碳电极微分计时电位溶出法测定DNA中的嘌呤碱基及DNA浓度

研究了鸟嘌呤(G)、腺嘌呤(A)、鸟嘌呤核苷、腺嘌呤核苷和变性DNA在电化学预处理玻碳电极上的恒电流微分计时电位溶出行为. 实验结果表明, 用电化学方法预处理玻碳电极操作简单, 效果明显, 预处理玻碳电极对嘌呤及其核苷和DNA的吸附能力大大增强, 用微分计时电位溶出法可以得到灵敏的溶出峰, 溶出峰高(dt/dE)与其浓度在一定范围内呈良好的线性关系, 可用于嘌呤碱基及其核苷的定量检测和DNA浓度的测定. 将该方法应用于酸变性DNA样品中鸟嘌呤与腺嘌呤的同时测定, 选择性好、灵敏度高; 还可获得有关DNA损伤的一些信息.     

活化碳布电化学传感器对尿酸的检测研究

使用新型柔性碳布(CC)电极,实现了中性、无酶环境下对人体尿酸(UA)的检测。使用循环伏安法(CV)研究尿酸在碳布上的氧化还原特性并直接测定尿酸的含量;使用差分脉冲伏安法(DPV)研究人体内常见物质对尿酸测定的影响。结果显示,在0.01 mol/L磷酸盐缓冲溶液(PBS,pH=7.4)中,尿酸的浓度在10～400μmol/L范围内与氧化峰电流具有良好的线性关系,相关系数为0.9981,检出限为4.083μmol/L。此传感器具有一定的抗干扰性和良好的重复性、稳定性,可用于实际样品中尿酸的检测,测定的回收率为99.6%～109.2%。     

基于壳聚糖/Ru（bpy）2+3/SiO2纳米粒子电化学发光传感器用于尿酸的检测

利用反相微乳液法制备了壳聚糖-Ru(bpy)2+3-SiO2复合纳米粒子,采用Nafion/MCNT复合膜技术实现了对复合纳米粒子有效而稳定的固定,从而制备了电化学发光传感器,实现了对尿酸的检测。在0.1 mol/L PBS缓冲溶液(pH 7.4)中,当尿酸与修饰电极作用15 min时,电化学发光强度与尿酸浓度(1.0×10-10~1.0×10-5 mol/L)的负对数呈良好的线性关系,线性方程为IECL=-709.52-202.74lgC,相关系数R=0.9936,检出限为6.0×10-12 mol/L。传感器表现出良好的重现性与稳定性,对1.0×10-8 mol/L尿酸平行测定11次,发光强度的相对标准偏差为2.9%,测定尿酸实际样品的加标回收率在98.5%~103.5%之间。     

纳米电化学界面的构建及脱氧核糖核酸中碱基对的电化学行为

以玻碳电极为基体,制备了单壁碳纳米管复合聚吖啶橙(SWNTs/POAO)修饰电极。此电极结合纳米材料电催化特性和吖啶橙聚合物薄膜的分子识别能力,以脱氧核糖核酸(DNA)分子中的碱基对为探针,研究了DNA中碱基对的电化学行为。该电极对腺嘌呤(ADE)、鸟嘌呤(GUA)、胞嘧啶(CYT)和胸腺嘧啶(THY)都表现了良好的电催化性,嘌呤碱和嘧啶碱的氧化峰能够完全分离。在pH 7.0的B.R.缓冲溶液中,在0.5~1.3V电位范围内,GUA和ADE分别在0.7V和1.0 V左右出现灵敏的氧化峰,峰电流随其浓度而线性变化。ADE和GUA的检出限分别为1.8×10-9和9.0×10-10mol/L。嘧啶碱基不干扰嘌呤碱基的测定。SWNTs/POAO电极可以用来同时测定DNA中的ADE和GUA。     

基于石墨烯和室温离子液体复合物溶胶修饰的玻碳电极制备尿酸电化学传感器

将石墨烯(GN)与室温离子液体(IL)1-丁基-3-甲基咪唑六氟磷酸盐(BMIMPF6),以适当比例研磨成胶状IL-GN,修饰在玻碳电极(GC)上制备了IL-GN/GC。利用原子力显微镜AFM表征IL-GN的形成。由于石墨烯和室温离子液体的协同作用,该电极显示了对H2O2良好的催化性能,基于尿酸氧化酶将之制备成生物传感器,用于尿酸(UA)直接电化学检测,并进行了传感器的抗干扰性能及实际血样中尿酸的检测实验。结果表明,此传感器检测尿酸的线性范围为0.002~4.5 mmol/L,相关系数为0.995,检出限为0.85μmol/L,响应时间为10 s。此传感器制备简便,稳定性好,抗干扰能力强,可用于实际血清中尿酸的检测,为尿酸的测定提供了新方法。     

合成2-氟腺嘌呤的新方法

从2-氨基-6-氯嘌呤出发,通过叠氮化反应合成2-氨基-6-叠氮嘌呤(3),3在希曼反应中完成氟对氨基的取代得到2-氟-6-叠氮嘌呤(4),4的叠氮基被还原为氨基制备出目标化合物2-氟腺嘌呤,总收率39.3%。     

Flow injection amperometric sensing of uric acid and ascorbic acid using the self-assembly of heterocyclic thiol on Au electrode

Au electrode modified with the self-assembled monolayer of a heterocyclic thiol, mercaptotriazole (MTz), is used for the electroanalysis of uric acid (UA) and ascorbic acid (AA). MTz forms a less compact self-assembly on Au electrode. The self-assembly of MTz on Au electrode favors the oxidation of UA and AA at less positive potential. Significant decrease (∼400 mV) in the overpotential and enhancement in the peak current for the oxidation of interfering AA with respect to the unmodified electrode is observed. The negative shift in the oxidation peak potential of AA favors electrochemical sensing of UA without any interference. Two well-separated voltammetric peaks for AA and UA are observed in their coexistence. The large separation between the two voltammetric peaks allows the simultaneous or selective sensing of the analytes without compromising the sensitivity. Linear response is obtained for a wide concentration range. This electrode could sense as low as 1 μM of UA in the presence of 10-fold excess of interfering AA. No change in the sensitivity (0.012 μA/μM) of the electrode toward UA in the presence and absence of AA is observed. Reproducible and stable amperometric flow injection response was obtained upon repetitive injection.     

Carbon Nanotube Immobilized Electrode Using Amphiphilic Phospholipid Polymer with Anti‐fouling and Dispersion Property for Electrochemical Analysis

A carbon nanotube (CNT)‐modified electrode was fabricated by dropping a dispersion of multi‐walled CNTs in water‐soluble and amphiphilic phospholipid polymer with both dispersing ability and anti‐biofouling property onto a Au electrode. A poly(2‐methacryloyloxyethyl phosphorylcholine‐co‐n‐butyl methacrylate) (PMB) composed from 50 mol% of 2‐methacryloxylethyl phosphorylcholine and 50 mol% of n‐butyl methacrylate (PMB50) was used as dispersing reagent for CNTs. The dispersion of water‐insoluble material by PMB50 and its antifouling effects in electrochemical analysis were investigated. The CNT‐modified electrode showed an anodic peak potential that was shifted negatively and an increase in the current value for the electrolytic oxidation of nicotinamide adenine dinucleotide. In addition, the charge on PMB50 did not inhibit the electrochemical reaction of the redox compounds K₃[Fe(CN)₆], [Ru(NH₃)₆]Cl₃, and hydroxymethylferrocene. Cyclic voltammetry of K₃[Fe(CN)₆] in 4 % bovine serum albumin (BSA) using a bare Au electrode, the anodic peak current was reduced to 47 % of that without BSA. In contrast, the antifouling effect of the PMB50‐coated electrode meant that the current was only reduced to 70 % of that without BSA.     

十六烷基三甲基溴化铵修饰碳糊电极线性扫描伏安法测定尿液中尿酸

本文提出了以十六烷基三甲基溴化铵修饰碳糊电极（CTAB／CPE）直接测定尿酸（UA）的新方法,用线性扫描伏安法（LSV）研究尿酸的电化学行为。在0.1mol／L磷酸盐缓冲溶液（PBS,pH=7.4）中,尿酸在CTAB／CPE上于0.160V处产生一个灵敏的氧化峰,氧化峰电流Ip与尿酸浓度（CuA）在1.0×10^-5—1.0×10^-3mol／L范围内呈良好的线性关系,相关系数为0.9940,检出限为1.0×10^-6mol／L。该方法简单实用,可以直接用于人体尿液中尿酸的检测。     

Determination of Uric Acid and Norepinephrine by Chitosan‐Multiwall Carbon Nanotube Modified Electrode

A novel chemically modified electrode based on the chitosan‐multiwall carbon nanotube (MWNT) coated glassy carbon electrode (GCE) is described, which exhibited an attractive ability to determine uric acid (UA) and norepinephrine (NE) simultaneously. The responses of UA and NE merged into a large peak at a bare GCE, but yielded two well‐defined oxidation peaks at the chitosan‐MWNT modified GCE (MC/GCE). The experimental parameters were optimized, and a direct electrochemical method for the simultaneous determine for UA and NE is proposed. The MC/GCE showed good sensitivity, selectivity and stability.     

A quadruplet electrochemical platform for ultrasensitive and simultaneous detection of ascorbic acid,dopamine, uric acid and acetaminophen based on a ferrocene derivative functional Au NPs/carbon dots nanocomposite and graphene

In this work, a new nanomaterial of thiol functional ferrocene derivative (Fc-SH) stabilized Au NPs/carbon dots nanocomposite (Au/C NC) coupling with graphene modified glassy carbon electrode (Fc-S-Au/C NC/graphene/GCE) was fabricated to serve as a quadruplet detection platform for ultrasensitive and simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and acetaminophen (AC). The Au/C NC was synthesized by adding HAuCl₄ into carbon nanodots solution without using any additional reductant and stabilizing agent. Then the Fc-SH was utilized as the protective and capping agent to modify the Au/C NC. Transmission electron microscopy (TEM), UV–Vis, Fourier-transform infrared (FT-IR), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) were adopted to characterize the morphology and electrochemical properties of the materials and the electrodes. The Fc-S-Au/C NC/graphene/GCE exhibits a synergistic catalytic and amplification effects towards oxidation of AA, DA, UA and AC owing to the existence of the nanomaterial and electron mediator. When simultaneous detection of AA, DA, UA and AC, the oxidation peak potentials of the four compounds on the electrode can be well separated and the peak currents were linearly dependent on their concentrations. The quadruplet detection platform shows excellent linear range and ultrasensitive response to the four components, the detection limits were estimated to be as low as 1.00, 0.05, 0.12 and 0.10 μM (S/N = 3), and the modified electrode exhibits excellent stability and reproducibility. The proposed electrode has been successfully applied to detect of these four analytes in real samples with satisfactory results.     

Simultaneous determination of uric acid, xanthine and hypoxanthine at poly(pyrocatechol violet)/functionalized multi-walled carbon nanotubes composite film modified electrode

A sensitive and selective electrochemical method was developed for simultaneous determination of uric acid (UA), xanthine (XA) and hypoxanthine (HX) based on a poly (pyrocatechol violet)/carboxyl functionalized multi-walled carbon nanotubes composite film modified electrode. The preparation and basic electrochemical performance of the novel composite film modified glassy carbon electrode were investigated in details. The electrochemical behaviors of UA, XA and HX at the modified electrode were studied by cyclic voltammetry. The results showed that this new electrochemical sensor exhibited excellent electrocatalytic activity towards the oxidation of the three analytes. The mechanism of catalysis was discussed. The anodic peaks of the three species were well defined with lowered oxidation potential and enhanced oxidation peak currents, so the modified electrode was used for simultaneous voltammetric measurement of UA, XA and HX by differential pulse voltammetry. Under the optimum conditions, the detection limits were 0.16 μmol L(-1) for UA, 0.05 μmol L(-1) for XA and 0.20 μmol L(-1) for HX, respectively (S/N of 3). The proposed method has been successfully applied to simultaneous determination of UA, XA and HX in human serum samples.     

Selective determination of uric acid in the presence of ascorbic acid using a penicillamine self-assembled gold electrode

The electrochemical behaviors of uric acid (UA) at the penicillamine (Pen) self-assembled monolayers modified gold electrode (Pen/Au) have been studied. The Pen/Au electrode is demonstrated to promote the electrochemical response of UA by cyclic voltammetry (CV). The diffusion coefficient D of UA is 6.97 × 10⁻⁶ cm² s⁻¹. In differential pulse voltammetric (DPV) measurements, the Pen/Au electrode can separate the UA and ascorbic acid (AA) oxidation potentials by about 120 mV and can be used for the selective determination of UA in the presence of AA. The detection limit was 1 × 10⁻⁶ mol L⁻¹. The modified electrode shows excellent sensitivity, good selectivity and antifouling properties.     

磷钨酸改性蒙脱土修饰电极对多巴胺与尿酸的测定

制作了磷钨酸改性蒙脱土修饰电极(PTA-MMT/GCE),研究了该电极对多巴胺(DA)和尿酸(UA)的电化学响应特性.结果表明:在pH 6.5的PBS缓冲溶液中,DA在该电极上出现1对氧化还原峰,是受扩散控制的可逆电化学过程;UA在该修饰电极上0.328 V处出现一明显的氧化峰,电极过程为受扩散控制完全不可逆的过程.计算了DA和UA在该修饰电极上的反应电子数n和扩散系数.通过对比改性前后修饰电极的交流阻抗图,研究了电极表面的特性.用循环伏安法讨论了缓冲溶液、pH值、修饰剂用量、扫描速率及温度对测定的影响.在pH 6.5的PBS溶液中,DA和UA的氧化峰得到了较好地分离,且DA、UA的峰电流强度与浓度分别在2.0～110.0和20.0 ～350.0 μmol·L-1范围内呈良好的线性关系.运用该电极对盐酸多巴胺注射液以及人尿进行检测,效果良好,样品回收率分别为94%～102%、93% ～97%.     

TiO2-石墨烯-Nafion复合膜修饰玻碳电极同时测定多巴胺和尿酸

利用在玻碳电极上修饰了TiO2-石墨烯-Nafion复合膜制得的修饰电极进行多巴胺(DA)和尿酸(UA)的同时测定。用循环伏安法(CV)和差分脉冲伏安法(DPV)研究了该修饰电极的电化学行为。在pH为7.0的磷酸盐缓冲液(PBS)中,修饰电极对于DA和UA的电化学氧化具有良好的电催化性能。DA和UA的氧化峰电流分别在2～120和60～300μmol/L浓度范围内呈良好的线性关系,检出限分别为0.066和0.102μmol/L。实验结果表明,TiO2-石墨烯-Nafion复合膜修饰电极显著提高了检测的灵敏度,并表现出良好的选择性和重现性。     

多巴胺在聚亚甲基蓝/石墨烯修饰电极上的电化学行为研究

利用电聚合方法在石墨烯修饰的玻碳电极表面制备了聚亚甲基蓝/石墨烯修饰电极(PMB/GH/GCE)。采用循环伏安法(CV)和差分脉冲伏安法(DPV)研究了多巴胺(DA)和抗坏血酸(AA)在该修饰电极上的电化学行为。在pH 6.9的磷酸盐缓冲溶液中,DA和AA分别在0.208 V和-0.108 V处产生灵敏的氧化峰,与其在聚亚甲基蓝和石墨烯单层修饰电极上的电化学行为相比,两者的峰电流明显增加,峰电位差达316 mV。研究表明,电聚合方法使亚甲基蓝牢固地非共价修饰到石墨烯上,并产生协同增效作用,较好地提高了电极的灵敏度和分子识别性能,有利于在大量AA存在下实现对DA的选择性测定。在1.00×10-3mol/L AA的存在下,DA的差分脉冲伏安法峰电流与其浓度在1.00×10-7～5.00×10-3mol/L范围内呈良好的线性关系,检出限达1.00×10-8mol/L。将该方法用于盐酸多巴胺注射液的测定,结果满意。