Trace determination of nitrated polycyclic aromatic hydrocarbons using liquid chromatography with on-line electrochemical reduction and fluorescence detection

An efficient clean-up procedure coupled with a high performance liquid chromatography (HPLC) with on-line electrochemical (EC) reduction and fluorescence detection (FLD) was developed to quantify nitrated polycyclic aromatic hydrocarbons (NPAHs) in the airborne particulate. In this process, NPAHs were extracted ultrasonically followed by analysis by using a reversed phase column with an aqueous eluent containing 70% aqueous acetonitrile and sodium monocholoroacetate as a buffer solution. The extraction efficiencies were above 83% for 1-nitropyrene and 1,3-dinitropyrene (1,3-DNP) 1,6-DNP, and 1,8-DNP, and calibration graphs were linear with very good correlation coefficients (r>0.999) and the detection limits were in the range of 1.0-2.2 pg for dinitropyrenes and nitropyrene. The proposed method provides a relatively simple and convenient procedure for determining the NPAHs samples in airborne particulate.     

Characterization of PEDOT film functionalized with a series of automated synthesis ferrocenyl-containing oligonucleotides

In previous works we have described a fully automated synthesis of new ferrocene labelled oligonucleotides (Fc-ODNs) probes with one or more electroactive markers at different position in the chain. These Fc-ODNs have shown good properties to detect ODN target in solution. Here we describe the post-functionalization of a conducting co-polymer based on ethylenedioxythiophene (EDOT) derivatives by a series of Fc-ODNs. The grafting of the Fc-ODNs probes resulted in the appearance of the ferrocene redox couple which directly confirm the effectiveness of the ODN anchoring compared to traditional approach based on IR spectroscopy and X-ray fluorescence of the films. Moreover, the electrochemical response of the modified electrodes analysed in organic media before and after hybridization with ODN target confirm that properties obtain in solution for Fc-ODNs already exist in the film. The changes in the current intensity were found to be dependant on the structure of the grafted ODN that validate our strategy to synthesize an optimal Fc-ODNs.     

Determination of Copper at a Glassy Carbon Electrode Modified with Langmuir–Blodgett Film of p‐tert‐Butylthiacalix[4]arene

A new type of voltammetric sensor, Langmuir–Blodgett film of p‐tert‐butylthiacalix[4]arene modified glassy carbon electrode, was advanced and used for determining copper at trace levels by differential pulse stripping voltammetry. Calibration plot was found to be linear in the range of 2×10^?8 M to 5×10^?6 M; the detection limit was 2×10^?9 M. Possible recognition mechanism was also discussed. From determination of Copper in real samples (river, lake and tap water) it can be concluded that the method is rapid, sensitive in determining of copper and can be used in the analysis of natural water samples.     

Determination of dopamine in synthetic cerebrospinal fluid by SWV with a graphite–polyurethane composite electrode

This work describes an electroanalytical investigation of dopamine using cyclic voltammetry (CV) and the graphite–polyurethane composite electrode (GPU). In CV studies, well-defined redox peaks characterize the oxidation process at the GPU electrode, which is indicative of electrocatalytic effects associated with active sites on the GPU electrode surface. A new analytical methodology was developed using the GPU electrode and square wave voltammetry (SWV) in BR buffer solution (0.1 mol L^–1; pH 7.4). Analytical curves were constructed under optimized conditions (f=60s^–1, E_a=50 mV, E_I=2 mV) and detection and quantification limits of 6.4×10^–8 mol L^–1 (12.1 g L^–1) and 5.2×10^–6 mol L^–1 (0.9 mg L^–1), respectively, were achieved. The precision of the method was checked by performing ten successive measurements for a 9.9×10^–6 mol L^–1 dopamine solution. For intra-assay and inter-assay precisions, the relative standard deviations were 1.9 and 2.3%, respectively. In order to evaluate the developed methodology, the determination of dopamine was performed with good sensitivity and selectivity, without the interference of ascorbic acid in synthetic cerebrospinal fluid, which indicates that the new methodology enables reliable analysis of dopamine.     

An LCEC method for the analysis of synthetic amino acids in fruit juices

Summary A fast and simple HPLC-method for the determination of synthetic amino acids in adulterated orange juice has been developed. The amino acid enantiomers were derivatized with a chiral reagent and the derivatives separated on a 3 m particle size C₁₈ column. An electrochemical detector operating in the oxidative mode was used for detection. The potential at which the derivatives are oxidized was determined by cyclic voltammetry.By using selective (electrochemical) detection it is possible to reduce the sample clean-up to simple centrifugation and filtration steps.     

无机胶体法制备Pt/C催化剂及其性能表征

采用无机胶体法制备用于质子交换膜燃料电池(PEMFC)的Pt/C催化剂。研究了影响PtO₂胶体生成和稳定性的因素(溶液的pH值、浓度和温度条件等)以及不同还原剂浓度对Pt/C催化剂性能的影响。透射电子显微镜测试结果表明，采用经优化的工艺条件所制备的Pt/C催化剂平均粒径为3 nm，且分散性好、粒度均匀。X-射线衍射分析表明，催化剂中Pt(111)晶面的相对含量较高，有利于加速氧还原反应。单体PEMFC的电压/电流密度曲线测试表明，所制备的Pt/C催化剂具有良好的电化学性能。     

1,8-亚乙基萘在三氟化硼乙醚-聚乙二醇中的电化学聚合

在三氟化硼乙醚(BFEE)-聚乙二醇(分子量400,PEG400)混合电解质溶液中,1,8-亚乙基萘直接阳极氧化聚合可以获得自支撑聚(1,8-亚乙基萘)膜.单体在三氟化硼乙醚+10%PEG400中的起始氧化电位为0.95 Vversus SCE,远低于单体在0.1 mol.L-1四氟化硼四丁基胺-乙腈溶液中的起始氧化电位(1.38 VversusSCE).同时PEG400的加入可以有效改善单体在三氟化硼乙醚中的溶解性.UV-Vis,FTIR和1H-NMR确定了1,8-亚乙基萘在4,5位聚合,荧光光谱表明固态及可溶聚(1,8-亚乙基萘)膜是蓝色发光材料.     

水相锌二次电池正极材料V2O5/C的电化学性能研究

采用溶胶－凝胶法合成了一种V₂O₅/C复合材料.扫描电镜（SEM）和红外光谱（FTIR）分析表明,这是一种外层V₂O₅胶体包覆内层乙炔分子的多孔复合材料.以V₂O₅/C作正极,锌片为负极,Zn(ClO₄)₂溶液为电解质组成水相锌二次电池,采用循环伏安（CV）和电化学阻抗谱（EIS）等方法研究发现:V₂O₅:C质量比为1:1时电极具有最好的电化学性能,电池开路电压达1.64 V; Zn^2＋能分别在1.01 V和1.26 V处分步嵌入V₂O₅/C结构中A、B两种位置,其嵌入电流密度峰值最高可达70 mA•g^－1,并且具有较好的循环充放电性能;在一定放电深度下,V₂O₅/C电极反应速率受Zn^2＋的扩散过程控制.     

Label-Free Impedance Biosensors: Opportunities and Challenges

Impedance biosensors are a class of electrical biosensors that show promise for point-of-care and other applications due to low cost, ease of miniaturization, and label-free operation. Unlabeled DNA and protein targets can be detected by monitoring changes in surface impedance when a target molecule binds to an immobilized probe. The affinity capture step leads to challenges shared by all label-free affinity biosensors; these challenges are discussed along with others unique to impedance readout. Various possible mechanisms for impedance change upon target binding are discussed. We critically summarize accomplishments of past label-free impedance biosensors and identify areas for future research.     

NdOx作为助催化剂对PtRu/C电催化氧化甲醇活性的影响

采用沉积-还原法制备了PtRu-NdOx/C催化剂, 借助TEM、EDS和XRD等测试手段对其进行了微结构和组成的表征. 结果表明, 催化剂中Pt与Ru以合金形式存在, 而Nd的氧化物则以无定形形态存在. 催化剂粒子的平均粒径在2 nm左右, 晶胞参数为0.3896 nm, Nd氧化物的加入对PtRu合金的晶体结构影响不明显. 采用循环伏安法和计时电流法, 比较了PtRu-NdOx/C催化剂和PtRu /C催化剂对甲醇氧化的电催化活性, 结果表明, 加入Nd的氧化物作为助催化剂能明显提高PtRu /C催化剂对甲醇氧化的电催化性能.