Determining Trace Concentrations of Copper in Water by Cathodic Film Stripping Voltammetry with Adsorptive Collection

Abstract

A technique is presented for the determination of trace concentrations of copper (II) in natural water samples by cathodic stripping voltammetry of a film of copper-catechol complex ions adsorbed on the hanging mercury drop electrode. The peak height of the copper-catechol reduction peak is linearly dependent upon the copper (II) concentration between 10^?10 and 10^?7 M. The detection limit of the technique is below 10^?10 M copper (II) for a collection time of 3 minutes, but the sensitivity can be further increased four-fold by collecting for 15 minutes. The sensitivity is reduced by high concentrations of competing trace metals and of surfactants, which necessitate the use of standard additions to the sample.     

Cathodic and Anodic Electroactive Product from Acidic Cleavage of Cepradine

Abstract

The isolation and identification of a cathodic degradation product from cephradine after acidic hydrolysis in presence of 1% formaldehyde is reported. Also, the electroactivity of an anodic degradation product is described. However, this product has not been identified.

Each electroactive product exhibits a diffusion-controlled polarographic wave and their respectives limiting currents show a linear dependence with the cephradine concentration. These characteristics are applied for analytical pur poses.

Synthetic samples exhibit 99.4 and 100.4% recoveries for the cathodic and anodic product respectively.     

GUIDING OF PLASMA BY ELECTRIC FIELD AND MAGNETIC FIELD

The relationship between the transported ion current and the cathodic arc current is determined in a vacuum arc plasma source equipped with a curved magnetic filter. Our results suggest that the outer and inner walls of the duct interact with the plasma independently. The duct magnetic field is a critical factor of the plasma output. The duct transport efficiency is to maximize at a value of bias plate voltage in the range +10 V to +20 V, and independent (within our limit of measurement) of the magnetic field strength in the duct. The plasma flux is composed of two components: a diffusion flux in the transverse direction due to particle collisions, and a drift flux due to the ion inertia. The inner wall of the magnetic duct sees only the diffusion flux while the outer wall receives both fluxes. Thus, applying a positive potential to the outer duct wall can reflect the ions and increase the output current. Our experimental data also show that biasing both sides of the duct is more effective than biasing the outer wall alone.     

复杂阴极保护体系三维有限元建模研究(英文)

滨海电厂常以天然海水作冷却水,其碳钢水室和钛管凝汽器在实施阴极保护过程中,要求钢电位应低于-0.85V(vs.SCE),电位过正则碳钢保护不足,而钛的电位则须高于-0.75V(vs.SCE),电位过负则易使钛管发生氢脆损伤.研究牺牲阳极阴极保护,需先得出两种金属在阴极保护过程中的电位分布.本文在设计室建立碳钢水室钛管模型,根据该实验体系阴极保护过程的(稳态极化和恒电流极化)测定获得两种金属有效的边界条件,用有限元(FEM)计算在一个牺牲阳极阴极保护状态得到三维电位分布.计算结果和测量结果基本一致,为优化阴极保护设计提供了理论依据.     

铜掺杂类金刚石纳米点阵列的制备及场发射性能研究

利用磁过滤等离子体结合氧化铝模板(AA0)技术在室温下制备了具有优异场发射性能的铜掺杂类金刚石(DLC)纳米点阵列.微观分析表明,铜掺杂类金刚石纳米点阵列分布均匀,密度高达109cm-2;利用X射线光电子能谱对制备的铜掺杂类金刚石纳米点阵列进行结构分析,测得铜的掺杂量为3.6;且sp3键含量高达60;;通过对铜掺杂类金刚石纳米点阵列的场发射性能测试,试验结果表明,铜掺杂类金刚石纳米点阵列开启电场和阈值电场分别为0.08V/μm,0.42V/μm,并且在电场值为0.67V/μm时,发射电流密度高达95mA/cm2,场发射性能明显优于无掺杂类金刚石纳米点阵列.     

Cathodic Adsorptive Stripping Voltammetric Determination of the Antitumor Drug Rutin in Pharmaceuticals, Human Urine, and Blood Serum

Cathodic adsorptive stripping voltammetry (CASV) was applied for the determination of rutin in pharmaceuticals, human urine, and blood serum. An electrochemical stripping procedure for trace measurements of rutin was developed based on the adsorption of the Cu²⁺-rutin complex on a hanging mercury drop electrode and applied to the quantification of the drug. Cyclic voltammetry was used to characterize the interfacial and redox behavior of the adsorbed Cu²⁺-rutin complex. Experimental and instrumental parameters for quantitative determination were optimized, and a detection limit of 4.9 × 10⁻⁹ mol · L⁻¹ in presence of Cu²⁺-ions for quantification of rutin under optimum conditions was derived. The sharp peak of the adsorbed Cu²⁺-rutin complex associated with an effective interfacial accumulation of this compound facilitates the determination of rutin in biological fluids with good recoveries. The degree of interference from potentially present metal ions and organic compounds on the CASV signal for Cu²⁺-rutin complex was evaluated.     

A validated stripping voltammetric procedure for quantification of the anti-hypertensive and benign prostatic hyperplasia drug terazosin in tablets and human serum

The electrochemical behavior of terazosin at the hanging mercury drop electrode was studied in Britton-Robinson buffer (pH 2-11), acetate buffer (4.5-5.5), and in 0.1 M solution of each of sodium sulfate, sodium nitrate, sodium perchlorate and potassium chloride as supporting electrolytes. The square-wave adsorptive cathodic stripping voltammogram of terazosin exhibited a single well-defined two-electron irreversible cathodic peak which may be attributed to the reduction of CO double bond of the drug molecule. A fully validated, simple, high sensitive, precise and inexpensive square-wave adsorptive cathodic stripping voltammetric procedure was described for determination of terazosin in bulk form, tablets and human serum. A mean recovery for 1×10⁻⁸ M terazosin in bulk form, following preconcentration onto the hanging mercury drop electrode for 60 s at a −1.0 V (versus Ag/AgCl/KCl_s), of 99±0.7% (n=5) was obtained. Limits of detection (LOD) and quantitation (LOQ) of 1.5×10⁻¹¹ and 5×10⁻¹¹ M bulk terazosin were achieved, respectively. The proposed procedure was successfully applied to determination of the drug in its Itrin^® tablets and human serum samples. The achieved LOD and LOQ of the drug in human serum samples were 5.3×10⁻¹¹ and 1.8×10⁻¹⁰ M THD, respectively. The pharmacokinetic parameters of the drug in human plasma were estimated as: C_max=77.5 ng ml⁻¹, t_max=1.75 h, AUC_0-t=602.3 ng h ml⁻¹, K_e=0.088 h⁻¹ and t_1/2=11.32 h) which are favorably compared with those reported in literature.     

银微盘电极上头孢氨苄降解产物的伏安行为及其应用

基于头孢氨苄降解产物中含有巯基，能与Ａｇ＾＋生成难溶化合物的特性，在银微盘电极上研究了ＣＥＸ降解产物的伏安行为，探讨了电极反应的机理。运用示差脉冲溶出伏安法，在０．１ｍｏｌ／Ｌ ＨＡｃ－ＮａＡｃ介质中，ＣＥＸ降解产物的还原峰电流与ＣＥＸ浓度于８．０×１０＾－８－７．０×１０＾－６ｍｏｌ／Ｌ范围内呈良好线性关系；检测限为１．０×１０＾０８ｍｏｌ／Ｌ；测定了头孢氨苄胶囊中ＣＥＸ含量为９２．０％，与药典     

生物小分子次黄嘌呤在银电极上的电化学性质

本文研究了银电极上次黄嘌呤的电化学特性。在含次黄嘌呤的醋酸～醋酸钠缓冲溶液中(pH3.7)，在0.35～0V电位区间内，银电极上出现一个还原峰，扫速50 mV/s时，其峰电位约在0.15V。该电极过程为单电子单质子过程。电化学和光谱电化学结果表明：这是由于次黄嘌呤与银形成难溶性化合物吸附于银电极表面而造成的。实验测得此难溶化合物的组成为1∶1，其溶度积为3.10×10^-7。用DPSV作阴极溶出分析，峰电流与次黄嘌呤浓度在8.0×10^-7～1.0×10^-     

Nanostructured cathodic catalysts for direct methanol fuel cells

The high activity of catalysts based of nanodisperse Pt-P system and their tolerance to the poisoning effect of methanol are demonstrated for the working potentials of cathodes in methanol-air fuel cells. The catalysts’ activity in the oxygen reduction reaction in the presence of methanol is nearly hundred times that of catalysts based on mixed metal-chalcogenide systems.