Fabrication of Poly(Aspartic Acid)-Nanogold Modified Electrode and Its Application for Simultaneous Determination of Dopamine, Ascorbic Acid, and Uric Acid

A nanostructured polymer film incorporated gold nanoparticles modified electrode was fabricated. The fabrication process involved a previous electropolymerization of aspartic acid and followed by the eletrodeposition of gold nano-particles on the glassy carbon electrode. The resulting poly (aspartic acid)-nanogold modified electrode (PAA- nano-Au/GCE) was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectros-copy (EIS). A higher catalytic activity was obtained to electrocatalytic oxidation of dopamine (DA), ascorbic acid (AA) and uric acid (UA) due to the enhanced peak current and well-defined peak separations compared with three, bare GCE, PAA/GCE and nano-Au/GCE. Simultaneous determination of DA, AA, and UA were studied by voltammetry. The linear range of 5.0 × 10-7 - 1.0 × 10-4 M for DA, 5.0 × 10-6 - 2.0 × 10-3 M for AA and 5.0 × 10-6 - 1.0 × 10-3 M for UA was obtained. The detection limit was calculated for DA, AA and UA as being 6.5 × 10-8 M, 5.6 × 10-7 M and 3.0 × 10-7 M, respectively (S/N = 3). The practical application of the present modified electrode was demonstrated by the determination of DA, AA and UA in calf serum and fetal calf serum samples.

Fe_3O_4 Magnetic Nanoparticles Modified Electrode as a Sensor for Determination of Nimesulide

A novel type of Fe3O4 nanoparticles modified glass carbon electrode（Fe3O4/GCE） was constructed and the electrochemical properties of N-（4-nitro-2-phenoxyphenyl）methanesulfonamide（nimesulide） were studied on the Fe3O4/GCE.In 0.4mol/L HAc-NaAc buffer solution（pH=5.0）,the electrode process of nimesulide was irreversible at bare GCE and Fe3O4/GCE.The Fe3O4/GCE exhibited a remarkable catalytic and enhancement effect on the reduction of nimesulide.The reduction peak potential of nimesulide shifted positively from-0.683 V at bare GCE to-0.625 V at Fe3O4/GCE,and the sensitivity was increased by ca.3 times.Some experimental conditions were optimized.The linear range between the peak current and the concentration of nimesulide was 2.6×10-6 ＂1.0×10-4mol/L（R=0.993） with a detection limit of 1.3×10-7mol/L.This method has been used to determine the content of nimesulide in medical tablets.The recovery was determined to be 96.9% ＂101.9% by means of standard addition method.The method is comparable to UV-Vis spectrometry.

Electrochemical Study and Application on Shikonin at Poly（diallyldimethylammonium chloride） Functionalized Graphene Sheets Modified Glass Carbon Electrode

The electrochemical behaviors of shikonin at a poly（diallyldimethylammonium chloride） functionalized graphene sheets modified glass carbon electrode（PDDA-GS/GCE） have been investigated. Shikonin could exhibit a pair of well-defined redox peaks at the PDDA-GS/GCE located at 0.681 V（Epa） and 0.662 V（Epc）[vs. saturated calo- mel electrode（SCE）] in 0.1 mol/L phosphate buffer solution（pH=2.0） with a peak-to-peak separation of about 20 mV, revealing a fast electron-transfer process. Moreover, the current response was remarkably increased at PDDA- GS/GCE compared with that at the bare GCE. The electrochemical behaviors of shikonin at the modified electrode were investigated. And the results indicate that the reaction involves the transfer of two electrons, accompanied by two protons and the electrochemical process is a diffusional-controlled electrode process. The electrochemical para- meters of shikonin at the modified electrode, the electron-transfer coefficient（a）, the electron-transfer number（n） and the electrode reaction rate constant（ks） were calculated to be as 0.53, 2.18 and 3.6 s^-1, respectively. Under the optimal conditions, the peak current of differential pulse voltammetry（DPV） increased linearly with the shikonin concentra- tion in a range from 9A72×10^-8 mol/L to 3,789×10^-6 mol/L with a detection limit of 3,157× 10^-8 mol/L. The linear regression equation was Ip=O.7366c＋0.7855（R=0.9978; lp： 10-7 A, c： 10-8 mol/L）. In addition, the modified glass carbon electrode also exhibited good stability, selectivity and acceptable reproducibility that could be used for the sensitive, simple and rapid determination of shikonin in real samples. Therefore, the present work offers a new way to broaden the analytical application of graphene in pharmaceutical analysis.

Detection of dopamine at graphene-ZIF-8 nanocomposite modified electrode

A hybrid graphene-ZIF-8（G-ZIF-8） nanocomposite modified electrode was prepared in our work. SEM characterization shows that nanocrystals of zeolitic imidazolate frameworks（ZIF-8） were homogeneously well-intergrown on the surface of graphene and thus the graphene sheets were refrained from restacking, which implies the high accessible surface area. The BET results further testifies that G-ZIF-8composites had a larger surface area than 3D graphene. G-ZIF-8 modified electrode exhibited excellent electroanalytical performance for dopamine. The linear concentration range was from 3.0 mmol/L to1.0 mmol/L with the detection sensitivity of 0.34 m A/mmol/L and the detection limit of 1.0 mmol/L was obtained. The interference study, electrode stability and reproducibility were carried out. In addition, the prepared sensor was applied to the detection of DA in serum sample with recoveries from 96.8% to100.7%. It is believable that the structure characteristic of G-ZIF-8 nanocomposite is favorable for using MOFs to fabricate highly sensitive electrochemical sensor

A nanosilica/exfoliated graphene composite film-modified electrode for sensitive detection of methyl parathion

Graphene nanosheets （GS） were easily prepared through liquid-phase exfoliation of graphite powder in N,N-dimethylformamide （DMF） with the assistance of sodium citrate. Then, GS was coated onto a glassy carbon electrode （GCE） surface by drop to fabricate a GS]GCE nanointerface. Subsequently, by using tetraethylorthosilicate sol as precursor, nanosilica was electrochemically deposited onto the GS]GCE surface to produce a nanocomposite film electrode （nanosilicaJGSJGCE）. Electrochemical behaviors of methyl parathion （MP） on the nanosilica/GS/GCE surface were investigated thoroughly. It was found that the nanosilicaJGS nanocomposites can improve the redox peak currents of MP significantly due to the synergetic effect. The oxidation peak current was linearly related to MP concentration in the range from 0.0005 μmol/L to 5.6 μmol/L. The detection limit was calculated to be 0.07 nmol/L （SJN = 3）. The developed method was used to determine MP in real samples. The recoveries were in the range from 95.4% to 104.2%, demonstrating satisfactory results.

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。

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 2 0 0 m V.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× 1 0 - 6 ～ 4 .0× 1 0 - 3 mol/L和 4 .0× 1 0 - 5 ～ 2 .0× 1 0 - 2 mol/L范围内与各自的浓度呈线性关系 ;检测限分别为 8.0× 1 0 - 7mol/L和 1 .0×1 0 - 5 mol/L.同时与导数伏安法一步测定进行比较 ,结果令人满意 .

二茂铁功能化石墨烯修饰电极用于多巴胺的检测

通过Friedel-Crafts酰基化反应制备二茂铁(Fc)功能化氧化石墨烯材料,利用透射电镜、傅里叶变换红外光谱和X-射线衍射对该复合物的形貌和结构进行了表征。将其滴涂到玻碳电极(GCE)表面并用Nafion膜固定,进行电化学还原,得到电化学还原氧化石墨烯复合材料修饰电极(Fc/ERGO/GCE)。此修饰电极对多巴胺的氧化还原具有良好的催化性能,在循环伏安曲线的0.2 V附近出现一对多巴胺的可逆氧化还原峰。差示扫描伏安法(DPV)峰电流大小与多巴胺浓度在0.4~300μmol/L范围内呈良好的线性关系(R2=0.9998),检出限为0.08μmol/L。用于检测人体尿液中的多巴胺含量,加标样品的回收率在92.5%~105.0%之间,相对标准偏差小于5%(n=5),表明制备的Fc/ERGO/GCE可用于实际样品中DA的检测。

聚合物修饰电极对多巴胺的电化学测定进展

多巴胺是哺乳动物中枢神经系统中的一种非常重要的信息传递物质,建立对多巴胺快速简单测定的分析方法非常重要。本文就05年以来聚合物修饰电极对多巴胺电化学检测的研究进展进行了综述。

双酚A在介孔碳修饰电极上的电化学行为及其测定

采用壳聚糖(CTS)作为有序介孔碳的分散剂,制备了有序介孔碳修饰玻碳电极(OMC/CTS/GCE)。用循环伏安法(CV)研究了环境激素双酚A在有序介孔碳修饰电极上的电化学行为。结果表明,介孔碳修饰电极对双酚A有强烈的电催化作用,在pH8.0的磷酸盐缓冲溶液(PBS)中,双酚A在0.479V处有1个明显的氧化峰,峰电流与双酚A浓度在4.5×10-8～1.2×10-5mol.L-1范围内呈良好的线性关系,检出限为2.0×10-8mol.L-1(S/N=3,n=8)。该法用于湖水样品中双酚A含量的测定,回收率为98%～104%,并与荧光法对照,测定结果吻合。

电化学还原氧化石墨烯/纳米金-壳聚糖复合膜修饰玻碳电极对尿酸的灵敏测定

将氧化石墨烯（GO）在玻碳电极（GCE）表面进行直接电化学还原，再组装上纳米金-壳聚糖（AuNP-CS）聚阳离子，形成了电化学还原氧化石墨烯/纳米金-壳聚糖（ERGO/AuNP-CS）复合膜修饰的玻碳电极。采用扫描电子显微镜（SEM）表征了不同修饰膜表面的形貌，探讨了其对尿酸（UA）分子的差分脉冲伏安（DPV）行为，发现ERGO/AuNP-CS复合膜对UA分子表现出显著的电催化氧化活性。在0.10mol/L磷酸盐缓冲溶液（pH=6.5）中，扫速为100mV/s时，此复合膜修饰电极的DPV响应与UA的浓度在0.05-110μmol/L范围内呈性关系，检测限为12.4nmol/L（S/N=3）。此修饰电极具有良好的选择性、重现性和稳定性，可应用于人体血清和尿液样品中UA的测定，回收率达到93.8%-104.1%。结果与分光光度法和尿酸酶试剂盒法相符。

尿酸在石墨烯修饰玻碳电极上的电化学行为及测定

以抗坏血酸为还原剂,采用微波水热法化学还原氧化石墨烯合成了石墨烯纳米片,制备了石墨烯修饰的玻碳电极(RGO/GCE),并采用循环伏安法、计时电量法、交流阻抗法等电化学技术研究了尿酸在该修饰电极上的电化学行为及其影响因素。结果表明,在PBS缓冲溶液中,尿酸(UA)在石墨烯修饰电极上的电极反应是一个受扩散控制的不可逆氧化过程。电极反应的转移电子数n=2,有效面积A=0.182 cm2,扩散系数D=1.51×10-6 cm2.s-1。UA的氧化峰电流与其浓度在5.0×10-6～1.5×10-4 mol/L范围内呈良好线性,r=0.995 7。利用该RGO/GCE修饰电极可以快速准确地测定UA,检出限为2.7×10-7 mol/L,加标回收率为98%～100%。

维生素C在多壁碳纳米管/壳聚糖复合膜修饰玻碳电极上的电化学行为及测定

研究了维生素C在多壁碳纳米管/壳聚糖复合膜修饰玻碳电极上的电化学行为及测定。实验结果表明,在0.2 mol/L PBS（pH6.0）缓冲溶液中,修饰电极对抗坏血酸的氧化具有明显的催化和增敏效应,其氧化峰电位由＋0.5 V负移至＋0.1 V（vs.AgCl/Ag）。对修饰剂碳纳米管的用量、支持电解质、富集电位和富集时间等进行了优化。采用半微分伏安法进行定量测定,其线性范围为4.0×10^-6~2.0×10^-3mol/L,r=-0.998 3,检出限为1.0μmol/L。对抗坏血酸在修饰电极上的电化学行为进行了探讨,其电极反应为具有吸附特性和不可逆的电极过程,测得参加反应的质子数为2,电极反应的电子转移系数为0.59。测定了维生素C药片中抗坏血酸的含量,回收率在93%~105%。

石墨烯修饰电极伏安法测定药物中的氧氟沙星

采用化学处理方法在石墨烯表面引入羟基和羧基等活性基团,并将其沉积在玻碳电极表面制作成氧化石墨烯修饰电极,然后运用循环伏安法研究了氧氟沙星在该修饰电极上的电化学行为。结果表明,该修饰电极对氧氟沙星的电化学氧化表现出较强的电催化作用。在最佳实验条件下,采用灵敏度较高的示差脉冲伏法测定了溶液中的氧氟沙星浓度,其浓度在7.5×10-7至1.0×10-4mol·L-1范围内与氧化峰电流呈良好的线性关系,相关相关系数r为0.9931,检出限为2.2×10-7mol·L-1(S/N=3)。在1h之内对含2.5×10-5mol·L-1氧氟沙星的溶液进行11次平行测定,相对标准偏差为3.6%,表明修饰电极的重现性和稳定性好。将该修饰电极用于氧氟沙星滴眼液中氧氟沙星含量的测定,平均回收率为98.2%。与其他方法相比,该方法简便、快速,灵敏度高,选择性好,可用于药物中氧氟沙星的分析。

石墨烯/聚苯胺复合膜修饰玻碳电极测定多巴胺

采用原位聚合法制备石墨烯／聚苯胺复合物，利用X射线衍射技术和红外光谱进行表征，通过滴涂法制备修饰电极，对多巴胺进行电化学测定。分别对支持电解质、pH值和扫描速率等实验条件进行了优化，建立了测定多巴胺的新方法。实验结果表明，经石墨烯／聚苯胺修饰后的玻碳电极对多巴胺具有很好的催化氧化作用。在0．1mol／L磷酸盐缓冲溶液中（pH值为4．0），多巴胺的线性响应范围为8．0×101～5．0×10-mol／L，相关系数为0．994，检出限为9．8×10～mol／L。该法用于实际样品中多巴胺的测定，回收率为97．19／6～103．4％。

聚L-精氨酸修饰电极存在下同时测定多巴胺和肾上腺素

用循环伏安法制备了聚L-精氨酸修饰玻碳电极，研究了多巴胺和肾上腺素在修饰电极上的电化学行为。建立了同时测定多巴胺和肾上腺素的新方法。在pH7．5的磷酸盐缓冲溶液中。多巴胺在修饰电极上产生一对氧化还原峰，峰电位分别为0．276V和0．059V；肾上腺素在修饰电极上产生3个氧化峰和一个还原峰，峰电位分别为0．262V、0．121V、-0．126V和-0．316V（对Ag／AgCl电极）。多巴胺和肾上腺素同时存在时△Epc=375mV，用还原峰对多巴胺和。肾上腺素同时测定的线性范围分别为8．0×10^-7～5．0×10^-4mol／L和5．0×10^-7～5．0×10^-5mol／L；检出限分别为3．0×10^-7mol／L和1．0×10^-7mol／L。大量的抗坏血酸和尿酸不干扰测定，用于人尿液中多巴胺和。肾上腺素样品的同时测定，结果满意。

基于石墨烯量子点修饰电极的亚硝酸根电化学传感器

文章将石墨烯量子点(GQDs)固载在裸玻碳(GC)电极表面形成石墨烯量子点修饰膜,制备亚硝酸根(NO_2^-)电化学传感器.利用透射电镜(TEM)和X-射线衍射(XRD)对石墨烯量子点材料进行表征;采用循环伏安(CV)、差分脉冲伏安(DPV)和电流-时间曲线(I-T)技术研究NO2-在石墨烯量子点修饰电极表面的电化学行为.实验结果表明,该电化学传感器对NO_2^-具有良好的电催化氧化性,在1~29μmol/L浓度范围呈现良好的线性关系,检出限为3.33×10^(-7) mol/L(S/N=3).该电化学传感器具有较宽的检测范围、低的检出限、好的选择性.

Nafion/胆碱双层膜碳纤维电极探测小白鼠大脑内的多巴胺

制备了胆碱（Ch）共价键植的碳纤维电极（Ch／CFE），进而吸附涂敷一薄层Nation膜得到了Nation／Ch／CFE。以循环伏安（CV）法和差分脉冲伏安（DPV）法研究了该电极上多巴胺（DA）的电化学响应。使用DPV法，该电极能良好抵抗代谢产物3，4-二羟苯乙酸（DOPAC）和抗坏血酸（AA）的干扰而选择性测量DA。在1．0mmol／LAA存在下，使用5mm长Nafion／Ch／CFE测定DA，检出限（S／N=3）为0．1μmol／L；线性范围为0．4—16μmol／L。该电极适于活体监测。将该电极插入小白鼠大脑纹状体内，实时监测了神经递质DA的浓度及其变化，观察到DA水平由静脉注射药物左旋多巴（L-DOPA）后随时间的响应，并发现针刺激对应于中医“风府穴”的头部皮下组织可引起脑内DA的即时性脉冲释放。

硫酸特布他林在石墨烯修饰电极上的电化学行为及应用分析

采用电化学阻抗法、循环伏安法、计时电量法、差分脉冲伏安法等分析手段,研究了硫酸特布他林在石墨烯修饰玻碳电极(GR/GC)上的电化学行为及电化学动力学性质,建立了硫酸特布他林电化学定量测定方法。实验结果表明,硫酸特布他林在GR/GC电极上的电化学过程是一个不可逆电化学氧化过程,氧化过程受扩散控制,在扫描速度20～250 mV/s范围内,其氧化峰电流与扫描速度平方根呈良好的线性关系。该方法可简便、快捷、灵敏地检测博利康尼中硫酸特布他林的含量。

基于十六烷基三甲基溴化铵存在下铅、银离子的高灵敏度电化学测定

报道了在适量十六烷基三甲基溴化铵 (CTMAB)存在下 ,高灵敏度测定水体中铅、银离子的化学修饰碳糊电极。在pH 2 .5 0 .1mol LKNO3溶液中 ,铅、银离子在钠型蒙脱石修饰碳糊电极上通过离子交换而富集 ,同时被还原。在阳极扫描过程中 ,分别在 - 0 .5 2V和 0 .2 3V(vs.SCE)处出现灵敏的溶出峰。详细研究了测定水样中铅、银离子的条件 ,如介质的pH、CTMAB用量、修饰剂用量、富集电位和时间等。该修饰电极连续测定铅、银离子的线性范围为 5 .0× 10 - 9mol L～ 1.0× 10 - 7mol L(Pb2 + )和 8.0× 10 - 9mol L～ 1.0× 10 - 7mol L(Ag+ ) ,富集 4min后检出限分别为 1.0× 10 - 1 0 mol L(Pb2 + )和 3.0× 10 - 1 0 (Ag+ )。