Determination of linuron in water and vegetable samples using stripping voltammetry with a carbon paste electrode

A carbon paste electrode was used for the electrochemical determination of linuron concentrations in water and vegetable extracts. Optimal conditions were established with respect to electrode activation (electrochemical pretreatment), time accumulation, potential accumulation, scan rate, and pH. The limit of detection achieved with a pre-concentration step was 23.0 μg L⁻¹. Recovery measurements in vegetable extract and natural water samples were in the range of 98-103%, indicating that the proposed electrochemical method can be employed to analyze linuron in these matrices. The determination results were in good agreement with HPLC results.     

超高效液相色谱-串联质谱法快速检测番茄酱中吡虫啉等6种农药残留

建立了番茄酱中吡虫啉、多菌灵、甲基硫菌灵、霜霉威、灭多威和烯酰吗啉等农药残留的超高效液相色谱-串联质谱(UPLC-MS/MS)检测方法。样品用含0.1%(体积分数)乙酸的甲醇-水(1:1, v/v)混合溶液提取,采用Waters Acquity UPLC BEH C18色谱柱,以甲醇和10 mmol/L乙酸铵溶液为流动相进行梯度洗脱分离,经电喷雾正离子(ESI+)电离及多反应监测(MRM)模式来测定目标化合物,采用基质标准溶液曲线法进行定量。结果表明: 6种农药在0.005～0.2 mg/L的范围内线性关系良好(r＞0.995);当标准添加水平为0.02、0.05和0.2 mg/kg时,回收率为66.8%～102.9%;相对标准偏差均小于15%; 6种农药的定量限（以信噪比（S/N）＞10计）均为0.02 mg/kg。该方法简便、快速、灵敏和准确,非常适合番茄酱中这6种农药残留的快速检测及定量分析。     

离子液体-Ni微/纳米粒子协同电催化检测维生素B2

本文制备了离子液体-Ni微/纳米粒子修饰碳糊电极.研究了离子液体对Ni微/纳米粒子氧化还原的促进作用,用循环伏安法在0.1 mol/L B-R缓冲溶液(pH=4.5)中研究了维生素B2(VB2)在该修饰电极上的电化学行为,优化了各种实验条件.实验结果表明,本文制备的修饰电极能很好地催化氧化VB2,VB2在该修饰电极上的...     

N‐(3,4‐Dihydroxyphenethyl)‐3,5‐dinitrobenzamide‐Modified Multiwall Carbon Nanotubes Paste Electrode as a Novel Sensor for Simultaneous Determination of Penicillamine,Uric acid,and Tryptophan

N‐(3,4‐dihydroxyphenethyl)‐3,5‐dinitrobenzamide modified multiwall carbon nanotubes paste electrode was used as a voltammetric sensor for oxidation of penicillamine (PA), uric acid (UA) and tryptophan (TP). In a mixture of PA, UA and TP, those voltammograms were well separated from each other with potential differences of 300, 610, and 310 mV, respectively. The peak currents were linearly dependent on PA, UA and TP concentrations in the range of 0.05–300, 5–420, and 1.0–400 µmol L^?1, with detection limits of 0.021, 2.0, and 0.82 µmol L^?1, respectively. The modified electrode was used for the determination of those compounds in real samples.     

Anodic Stripping Voltammetric Determination of Iron(II) at a Carbon Paste Electrode Modified with Dithiodianiline (DTDA) and Gold Nanoparticles (GNP)

A differential pulse anodic stripping voltammetric procedure was developed for the determination of trace amounts of iron(II) in the presence of iron(III) at a carbon paste electrode (CPE) modified with dithiodianiline and gold nanoparticle. At the pH working of 3.0, a wide concentration range from 0.1 nM to 100 nM was observed with the detection limit of 0.05 nM. The relative standard deviation for a solution containing 50 nM of iron(II) was found to be 3.11 % (n=9). Possible interferences from the coexisting ions were also investigated. The validity of the method and applicability of the sensor were successfully tested by determining of iron(II) in lentil, wheat seed and barley seed samples.     

A strategy for constructing sensitive and renewable molecularly imprinted electrochemical sensors for melamine detection

A novel strategy for preparing highly sensitive and easily renewable molecularly imprinted polymer (MIP) sensors was proposed. Using melamine (MA) as the template molecule, MIP particles were synthesized and embedded in a solid paraffin carbon paste to prepare the MIP sensor. MA was indirectly determined from the competition between the reactions of MA and horseradish peroxidase-labeled MA (MA-HRP) with the vacant cavities. The detection signals were amplified because of enzymatic reaction to the H₂O₂ catalytic oxidation. Sensitivity was markedly improved. Sensor renewal was achieved by a simple mechanical polishing of the sensitive film. The linear range for MA detection was 0.005–1 μmol L⁻¹ and the detection limit was 0.7 nmol L⁻¹. The molecularly imprinted solid paraffin carbon paste sensor was used for MA detection in milk samples.     

Electrochemical studies of determination of C.I. Direct Red 80 based on a gold nanoparticles-modified carbon paste electrode

In this paper, a simple, convenient and sensitive electrochemical method has been developed for the determination of C.I. Direct Red 80. A gold nanoparticle modified carbon paste electrode was fabricated and used for study and sensitive determination of Direct Red 80 by cyclic voltammetry and differential pulse voltammetry. The overall analysis involved a two-step procedure: an accumulation step under open-circuit conditions, followed by voltammetric measurements of Direct Red 80 in a 0.1?M phosphate buffer solution at pH?=?3.0. The experimental conditions, such as the medium, pH and accumulation time, were optimised. The oxidation peak current was proportional to the concentration of Direct Red 80 from 5.0?×?10^?8 to 5.0?×?10^?7?M and 5.0?×?10^?7 to 3.0?×?10^?6?M, and the detection limit was 1.15?×?10^?8?M (S/N?=?3). The proposed method was used to detect Direct Red 80 in natural water and sewage with good accuracy.     

A new voltammetric sensor for the determination of sulfite in water and wastewater using modified-multiwall carbon nanotubes paste electrode

The electrochemical response of a modified-carbon nanotubes paste electrode with p-aminophenol was investigated as an electrochemical sensor for sulfite determination. The electrochemical behaviour of sulfite was studied at the surface of the modified electrode in aqueous media using cyclic voltammetry and square wave voltammetry. It has been found that under the optimum condition (pH 7.0) in cyclic voltammetry, the oxidation of sulfite occurs at a potential about 680?mV less positive than that of an unmodified-carbon nanotubes paste electrode. Under the optimized conditions, the electrocatalytic peak current showed linear relationship with sulfite concentration in the range of 2.0?×?10^?7–2.8?×?10^?4?mol?L^?1 with a detection limit of 9.0?×?10^?8?mol?L^?1 sulfite. The relative standard deviations for ten successive assays of 1.0 and 50.0?µmol?L^?1 sulfite were 2.5% and 2.1%, respectively. Finally, the modified electrode was examined as a selective, simple and precise new electrochemical sensor for the determination of sulfite in water and wastewater samples.     

Novel potentiometric sensor for the determination of Cd2+ based on a new nano-composite

A novel ion selective carbon paste electrode for Cd²⁺ ions based on 2,2′-thio-bis[4-methyl(2-amino phenoxy) phenyl ether] (TBMAPPE) as an ionophore was prepared. The carbon paste was made based on a new nano-composite including multi-walled carbon nanotubes (MWCNTs), nanosilica and room-temperature ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆). The constructed nano-composite electrode showed better sensitivity, selectivity, response time, response stability and lifetime in comparison with typical Cd²⁺ carbon paste sensor for the successful determination of Cd²⁺ ions in water and in waste water samples. The best performance for nano-composite sensor was obtained with an electrode composition of 18% TBMAPPE, 20% BMIM-PF₆, 48% graphite powder, 10% MWCNT and 4% nanosilica. The new electrode exhibited a Nernstian response (29.95?±?0.10?mV?decade^?1) toward Cd²⁺ ions in the range of 3.0?×?10^?8 to 1.0?×?10^?1?mol?L^?1 with a detection limit of 7.5?×?10^?9?mol?L^?1. The potentiometric response of prepared sensor was independent of the pH of test solution in the pH range 3.0 to 5.5. It had a quick response with a response time of about 6?s. The proposed electrode showed fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions.     

基于量子点涂料的柔性光阳极及碳基对电极的制备和优化

首先制备出量子点（QDs）/TiO₂涂料,分别采用丝网印刷法与刀刮法将涂料涂覆于ITO/PET柔性基底上,结果表明刀刮法制备量子点敏化太阳电池（QDSCs）效果更佳,且具有普适性。基于铜片对电极所组装的ZnCuInSe,CdSe和CdSeTe量子点半柔性QDSCs最高效率分别达2.83%,2.46%和1.99%。另外,我们对石墨纸进行表面化学修饰以提高亲水性,再通过简单的连续离子交换吸附法（SILAR）在石墨纸上负载Cu_xS纳米粒子,制备出Cu_xS/GP柔性对电极,进一步组装成全柔性QDSCs,获得了2.13%光电转化效率。