Water-Miscible Room-Temperature Ionic Liquid-Cobalt Hexacyanoferrate Gel Modified Electrode for Electrocatalytic Oxidation of NADH.

Cobalt hexacyanoferrate particles were ground with water-miscible room-temperature ionic liquid, 1-methylimidazolium trifluoroacetic acidic salts (HMImTfa), and resulted in HMImTfa-CoHCF gel. The electrochemical properties of HMImTfa-CoHCF gel were investigated in detail. The impedance data show that HMImTfa-CoHCF gel is mixed ionic-electronic and has 2.5 times the improvement of the conductivity than that of pure HMImTfa. HMImTfa-CoHCF gel can be used in chemically modified electrode for the electrocatalytic oxidation of NADH. The corresponding results have important implications for the design of nano-structured and nano-composite materials based on water-miscible room-temperature ionic liquids, which could be used widely in chemo/biosensing and catalysis.</p

Flow-Injection Analysis (FIA) Electrochemical Speciation of Copper in Coastal Waters by Anodic Stripping Voltammetry (ASV)

A sensitive and precise method for copper (Cu) speciation [electroactive Cu (II), acid-dissolved Cu (0, II), and inert Cu (0)] in coastal waters was developed using flow-injection analysis and electrochemical detection. The reaction is based on a simple redox reaction using a gold nanoparticle modified electrode. The effects of experimental parameters were investigated and optimized. The presence of iron, lead, zinc, cadmium, and aluminum did not interfere with the determination of copper. For total copper, the method detection limit was 1.3 nM, and the quantification range was from 5 to 1000 nM (R(2)equal to 0.995), which is sufficiently sensitive for coastal water analysis. A certified reference material was used to characterize the accuracy and good agreement was obtained. The developed method was applied to analyze coastal water samples collected from the Guangdang River, Shandong, China. The Cu species present are reported and discussed

A functional micro-needle sensor for voltammetric determination of iron in coastal waters

A novel micro-needle sensor based on gold nanoclusters (AuNCs) immobilized with conducting polymer film poly (3,4-ethylenedioxythiophene)-poly(sodium 4-styrenesulfonate) (PEDOT-PSS) was fabricated for determination of iron in coastal waters. The unique aciform structure of the micro-needle electrode (MNE) provided larger specific surface area than common electrodes. The surface modification of MNE with PEDOT-PSS improved the conductivity of the electrode and increased the active sites for combination and immobilization of AuNCs. The cluster-like structure of AuNCs was formed as a result of the regulation of PEDOT-PSS, which showed excellent electrocatalytic activity for the reduction of Fe3+. The so-fabricated AuNCs/PEDOT-PSS/MNE showed excellent sensitivity, selectivity, reproducibility, and repeatability for iron determination with the linear range of 0.01-5 mu M and detection limit of 3.1 nM, respectively. Furthermore, the micro-needle sensor was successfully used for the determination of acidified dissolved iron in a coastal river from the source to the estuary with satisfactory results

Detection of Cu2+ in Water Based on Histidine-Gold Labeled Multiwalled Carbon Nanotube Electrochemical Sensor

Based on the strong interaction between histidine and copper ions and the signal enhancement effect of gold-labeling carbon nanotubes, an electrochemical sensor is established and used to measure copper ions in river water. In this study the results show that the concentrations of copper ion have well linear relationship with the peak current in the range of 10−11–10−7 mol/L, and the limit of detection is 10−12 mol/L. When using this method to detect copper ions in the Xiangjiang River, the test results are consistent with the atomic absorption method. This study shows that the sensor is convenient to be used in daily monitoring of copper ions in river water

New application of tin-bismuth alloy for electrochemical determination of cadmium

Electrochemical properties of commercial tin-bismuth alloy were investigated and the tin-bismuth alloy based electrode was used for stripping voltammetric determination of cadmium (Cd2+) for the first time. Electrodeposition and electrochemical stripping of Cd2+ on tin-bismuth alloy electrode (SnBiE) were implemented and the results with an excellent linear dynamic range of 5-500 nM, a correlation coefficient of 0.999 and a detection limit of 1.1 nm were obtained under the optimal experimental conditions. It revealed that not only does this environment friendly alloy electrode material have a high hydrogen overvoltage and relatively wide potential window, but also has excellent repeatability and reproducibility. The practical application was carried out for the determination of Cd2+ in food samples and the results were consistent well with those by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).Electrochemical properties of commercial tin-bismuth alloy were investigated and the tin-bismuth alloy based electrode was used for stripping voltammetric determination of cadmium (Cd2+) for the first time. Electrodeposition and electrochemical stripping of Cd2+ on tin-bismuth alloy electrode (SnBiE) were implemented and the results with an excellent linear dynamic range of 5-500 nM, a correlation coefficient of 0.999 and a detection limit of 1.1 nm were obtained under the optimal experimental conditions. It revealed that not only does this environment friendly alloy electrode material have a high hydrogen overvoltage and relatively wide potential window, but also has excellent repeatability and reproducibility. The practical application was carried out for the determination of Cd2+ in food samples and the results were consistent well with those by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). (C) 2011 Elsevier B.V. All rights reserved

Determination of Trace Copper in Water Samples by Anodic Stripping Voltammetry at Gold Microelectrode

The applicability of gold microelectrode of 25 mu m diameter for electrochemical determination of trace copper ions (Cu(2+)) in water samples by anodic stripping voltammetry (ASV) has been demonstrated. The analysis of Cu(2+) at gold microelectrode includes two steps. Cu(2+) ions are firstly reduced and accumulated on the microelectrode surface during an accumulation step, then oxidized during the positive potential sweep. Due to the rapid mass transporting and low background current of gold microelectrode, low detection limit (0.3 nM) and wide linear range (1.0-90 nM) can be obtained. The practical application of gold microelectrode was verified by determination of trace level of Cu(2+) in tap water, lake water and commercial drinking water samples

Adsorbent-Assisted In Situ Electrocatalysis: Highly Sensitive and Stable Electrochemical Sensor Based on AuNF/COF-SH/CNT Nanocomposites for the Determination of Trace Cu(II)

The weak conductivity of covalent organic frameworks (COFs) limits their wide application in electrochemical sensors. Here, a novel electrochemical sensor (AuNFs/COF-SH/ CNTs/GCE) was designed and constructed by a one-step electrochemical deposition of Au nanoflowers (AuNFs) on a hybrid nanocomposite of sulfhydryl-functional covalent organic framework/carbon nanotubes (COF-SH/CNTs) for the determination of Cu(II) in seawater. AuNFs/COF-SH/CNTs/GCE was prepared in a three-step method including in situ synthesis, post synthesis, and one-step electrochemical deposition. The adsorption and catalytic performances of the modified electrode were improved based on the mechanism of ???adsorption-catalysis stripping determination???. By combining the excellent catalytic properties of the AuNFs with the good adsorption capacity of COF-SH toward Cu(II), as well as the good conductivity of CNTs, the AuNFs/COF-SH/CNTs/GCE exhibited excellent performance for the determination of Cu(II). Through optimization of the experimental conditions, a low detection limit of 0.47 nM and a wide linear range of 1.6 nM-4.7 ??M were obtained. Moreover, the sensor possessed good stability with a relative standard deviation of less than 5% after 20 repeated measurements. The results are consistent with certified values when used for the determination of certified reference materials. In summary, the AuNFs/COF-SH/CNTs/GCE, with high stability and sensitivity, has been successfully applied for the determination of Cu(II) in seawater samples with satisfactory results

Nafion assisted preparation of prussian blue nanoparticles and its application in electrochemical analysis of L-ascorbic acid

Due to the high sensitivity, simplicity and low cost, electrochemistry methods based on nanoparticles have been considered as an attractive technique for L-ascorbic acid. Herein, prussian blue nanoparticles (PBNPs) were synthesized by a fast and convenient synthesis strategy with Nafion and K4[Fe (CN)(6)] 3H2O. The PBNPs have uniform grain size of about 11.9 nm. PBNPs modified glassy carbon electrode (GCE) was used to construct electrochemical sensor for L-ascorbic acid (AA) detection and the optimization condition was studied. The electrochemical results indicate that PBNPs/GCE sensor shows a linear response to L-ascorbic acid in the range of 1-1100 mu M with a detection limit of 0.47 mu M and sensitivity of 22.9 mu A.mM(-1).cm(-2) at a working potential of 0.24 V (vs. SCE). The stability and reproducibility of the same PBNPs/GCE are RSD = 0.7% and RSD = 1.3%, respectively. The excellent characteristics of this sensor demonstrates it is a useful tool for accurate determination of L-ascorbic acid in medicine samples such as a vitamin C tablet and for Vitamin C chewable tablets

Speciation determination of iron and its spatial and seasonal distribution in coastal river

Abstract In this study, the speciation of iron (Fe), including total Fe (TFe) and acidified dissolved Fe (ADFe), was assessed by fast cathodic absorption stripping voltammetry, using a gold electrode and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) as a novel complexing agent for Fe. The validity and accuracy of this method were compared with the standard spectrophotometry and tested by the standard samples. Under optimized conditions, the Fe response was linear within the range of 0.01 to 1 μM with a detection limit of 1.2 nM. To further validate this method, the variation in concentrations of TFe and ADFe were investigated at twelve sampling stations in a local coastal river, in both the dry and wet season. Additionally, to further understand the interaction between Fe and environmental factors, the relationships between the concentration of Fe species and dissolved oxygen (DO) and salinity were also discussed