Determination of Melphalan Using Differential Pulse Voltammetry

Abstract

The anodic oxidation of melphalan was studied on a glassy carbon disk electrode, either stationary or rotated, using a d.c. and a differential pulse potential program. The conditions have been found for a differential pulse voltammetric determination of the substance, with a detection limit of 1 × 10^?6 mol 1^?1     

差分脉冲伏安法测定卡托普利

本文基于金电极表面对巯基化合物的吸附作用,提出了一种简便灵敏的测定抗高血压药物卡托普利的新方法.研究了卡托普利在金电极上的伏安响应,优化了差分脉冲伏安法测定卡托普利的实验条件.研究结果表明:在0.217～3.04 mg/L的范围内,卡托普利的氧化峰电流与其浓度呈良好的线性关系,检出限为0.152 mg/L.测定药物中卡...     

Simultaneous Determination of Trace Zinc(II) and Cadmium(II) by Differential Pulse Anodic Stripping Voltammetry Using a MWCNTs–NaDBS Modified Stannum Film Electrode

A multiwalled carbon nanotubes–sodium dodecyl benzene sulfonate (MWCNTs–NaDBS) modified stannum film electrode was employed for the determination of cadmium(II) and zinc(II). The Sn/MWCNTs‐NaDBS film electrode was prepared by applying MWCNTs–NaDBS suspension to the surface of the GCE, while the Sn film was plated in situ simultaneously with the target metal ions. Under optimal conditions, linear calibration curves were obtained in a range of 5.0 ?100.0 μg L^?1 with detection limits of 0.9 μg L^?1 for zinc(II) and 0.8 μg L^?1 for cadmium(II), respectively. This film electrode was successfully applied to the determination of Zn(II) and Cd(II) in tap water sample.     

A Study of The Cadmium(II) Trimethylenediamine Complexes By Differential Pulse Polarography

Abstract

The overall formation constants of the Cd (Trimethylene-diamine) system were determined by differential pulse polarography at 25°C and at μ = 1 (NaNO₃). The percentage distribution of cadmium present in various forms as a function of ligand concentration was calculated.     

Electrochemical Behaviour Study of Mixed Ligand Complexes of Diaminopropane and Phthalate with Cd(II) Using Differential Pulse Polarography and Cyclic Voltammetry Techniques

Abstract

Differential pulse(d. p.)polarography has been used to study the simple and mixed ligand complexes of 1, 3 diaminopropane (DAMP) and phthalate(PHLT) with Cd(II) at constant ionic strength (u= 1.0 M NaNO₃) at 25°C The overall formation constants of simple and mixed complexes were calculated. The reduction of the simple and mixed species is reversible and diffusion controlled. The postive values of the mixing constants for the mixed-ligand complexes indicate that the mixed-ligand complexes are more stable than simple binary complexes. The equilibria between the various mixed-ligand species in the solution and their equilibrium are given.     

Mössbauer Spectroscopic Determination of Stability Constants of Fluorostannate(II) Complexes

Stability constants of fluorostannate(II) complexes were determined Mössbauer spectroscopically by rapid freezing technique. The observed isomer shift values suggested that these complexes were hydrogen bonded in perchloric acid solutions.     

石墨烯基纳米复合物修饰印刷电极伏安法测定水中镉

构建了基于石墨烯(GS) -纳米金(Au)复合纳米微粒修饰印刷电极(SPCEs)的电化学传感器(SPCEs |GS/Au),建立了微分脉冲溶出伏安(DPSV)法测定水中痕量镉的电分析方法.采用扫描电镜(SEM)对电极表面进行了表征,DPSV法研究了镉的电化学性质.在优化实验条件下,溶出峰电流与Cd2+的质量浓度在2.5...     

Determination of Cadmium by Differential Pulse Adsorptive Stripping Voltammetry in the Present of Captopril

A new method is presented for determination of cadmium based on cathodic adsorptive stripping of the complex of cadmium with captopril,1‐[(2S)‐3‐mercapto‐2‐methylpropionyl]‐L ‐praline (CPL) at a hanging mercury drop electrode(HMDE). The most suitable operating conditions and parameters, such as pH, deposition potential, deposition time, ligand concentration, and others were selected and the determination of cadmium from aqueous solutions using the standard additions method was possible. Under the optimum conditions and for an accumulation time of 60 s, the measured peak current is proportional to the concentration of cadmium over the range of 1–300 nM. The limit of detection at S/N ratio of 3 was 0.3 nM and a relative standard deviation of 2.5% at 0.1 μM was achieved. The interference of other cations and anions was studied. The method was designed in order to determination of Cd in four analytical grade salts, with satisfactory results.     

Prediction of Stability Constants for Cr(III) and Cr(II) Complexes

Regression analysis was used to derive equations for estimaing thermodynamic stability constants for complexes of Cr²⁺ (log^° ₁[Cr²⁺L] = 0.53log^° _n [H _n L]) and Cr³⁺ (log^° ₁[Cr³⁺L] = 0.88log^° _n [H _n L]) from the known protonation constants of H _n L ligands and for determining stability constants of Cr²⁺ and Cr³⁺ complexes from the available stability constants of Cu²⁺ complexes (log^° ₁[Cr²⁺L] = 0.76log^° ₁[Cu²⁺L] and log^° ₁[Cr²⁺L] = 0.60log^° ₁[Cr³⁺L], respectively). Parameters of the Panteleon–Ecka equation for calculating stability constants of Cr²⁺ complexes ( = 0.57) and Cr³⁺ complexes ( = 0.69) with two and three bidentate ligands were also determined. The ratio of logarithmic stability constants for complexes with the same metals but with different metal ionic charges was found to be approximately equal to the ratio of charges on the central ions. The stability constant of Cr(II) sulfate complex was calculated.     

Determination of Stability Constants of Metal(II)-Methionine and Metal(II)-Methionine-Cysteine (Binary and Mixed) Complexes with a Paper Ionophoretic Technique

A mixed complexation reaction of methionine and cysteine with copper(II) and cobalt(II) has been studied in solution phase using the paper electrophoretic technique at ionic strength 0.1 M and a temperature of 35°C. The binary equilibria copper(II)-methionine and cobalt(II)-methionine have also been studied, since this is prerequisite for the investigation of mixed complexes. The stability constants of copper(II)-methionine-cysteine and cobalt(II)-methionine-cysteine mixed complexes were found to be 2.80 ± 0.07 and 2.44 ± 0.11 (logarithm of stability constant values), respectively. This article was submitted by the authors in English.     

差分脉冲溶出伏安法测定陶瓷器皿中铅和镉的溶出率

采用4%的乙酸浸泡陶瓷样品24 h,应用同位镀汞差分脉冲溶出伏安法测定了陶瓷样品中微量重金属铅、镉的溶出量。以0.1 mol/L的硝酸溶液做底液,0.1 mol/L的KCl溶液做支持电解质,2 g/L的Hg2+溶液做镀汞液,测得铅的溶出峰电位为-0.5 V(vsSCE),镉的溶出峰电位为-0.7 V(vsSCE),两者含量在5×10-4～1 mg/L和5×10-4～0.5 mg/L范围内峰电流和其含量呈良好的线性关系,检出限分别为2×10-4和4.3×10-3mg/L。     

Determination of Stability Constants for Complexes of Ni(II) with Adenine and Guanine from Catalytic Linear Scan Voltammetric Currents

The catalytic effects of adenine and guanine on the reduction of Ni(II) at the hanging mercury drop electrode were used to study the formation of complexes in the bulk of aqueous solutions at 25 °C and ionic strength 0.2 M. Complexation data were obtained from an analysis of the kinetic (catalytic) pure limiting currents, according to a method proposed previously. Values of 3.70 and 3.17 were determined for the logarithms of the stability constants corresponding to the formation of 1 : 1 complexes between Ni(II) – aquo ion and the neutral form of adenine and guanine, respectively.     

Determination of Paraquat Dichloride from Water Samples Using Differential Pulse Cathodic Stripping Voltammetry

Paraquat dichloride commonly used as herbicide was determined by differential pulse cathodic stripping voltammetry technique. Experimental parameters, such as pH, accumulation time, accumulation potential and initial potential were optimized. In this analysis, paraquat dichloride exhibited a well-defined tworeduction peaks at ?0.35 and ?0.90 V in the pH range from 2.0 to 12.0. The 0.04 mol L^–1 BR buffer at pH 2.0 was found a suitable medium for electroanalytical determination of the paraquat dichloride. Interfering ions effect was not significant. Linear calibration plots for standard solutions of paraquat dichloride were obtained in the range of 0.25 to 1.75 × 10^–6 mol L^–1. Detection limit was 3.66 × 10^–8 mol L^–1. The optimized parameters were effectively applied for the determination of commercial paraquat dichloride and in artificial samples. Artificial samples were prepared by spiking paraquat dichloride into tap water and drinking water dispenser samples. The recovery value was 90.5% in drinking water dispenser samples and 91.7% in tap water samples at the concentration range of 1.00 × 10^–6 to 1.75 × 10^–6 mol L^–1.

     

Studies on Mixed Complexes of Cd(II) With Trimethylenediamine and Succinate Using Differential Pulse Polarography

Abstract

Ternary compleres of cadmium (II) with succinate (Succ) as primary ligand and trimethylenediamine (TMDA) as secondary ligand have been studied using differential pulse polarography. Schaap and McMasters treatment reveals the presence of three mixed complexes with stoichiometries 1:1:1, 1:1:2 and 1:2:1. The reduction is reversible and diffusion-controlled. The stability constants of mixed ligand complexes were calculated atatistically using watters method and compared with the observed values.     

Differential Pulse Polarography of the Cadmium(II)-Imidazole Complex System

Abstract

A differential pulse polarographic study of the complexation of cadmium(II) with imidazole gives the relationship, Ej/₂ = -0.798 – 0.132 log [imidazole]_t for the cadmium(II) half wave potential (E]/₂) with imidazole concentration. Also, the differences between the half-wave potentials (ΔEj/₂) of the complex and metal ion have been used to determine log g_n (6.75) and coordination number (4) for the cadmium-imidazole complex according to Subrahmanya's method.     

Determination of Cobalt Ions in Natural Waters Using Differential Pulse Adsorptive Stripping Voltammetry

Abstract

Differential pulse adsorptive stripping voltammetry using dimethylglyoxime complexes in the presence of triethanolamine and ammonium chloride can be applied to the determination of cobalt (II) ions in natural waters with high sensitivity. The limit of detection is about 3 ppt. Actual analysis of estuary water are reported. In this particular case of natural water, the factors influencing the use of differential pulse adsorptive stripping voltammetry for the determination of cobalt are described in detail.     

Concentration and Thermodynamic Stability Constants of Magnesium(II) and Calcium(II) Tartrate Complexes in Aqueous Solutions

The formation of calcium and magnesium tartrate complexes was studied by potentiometric titration at ionic strengths of 0.1 and 0.3 (in the presence of tetraethylammonium chloride) at a temperature of 298.15 K. The composition and the stability constants of the complexes formed in the system were determined. The known stability constants were used to optimize the conditions of calorimetric determination of the heats of formation of calcium and magnesium tartrates in an aqueous solution.     

离子交换伏安法同时测定水体中的镉、汞

报道了一种同时快速测定水体中痕量镉、汞的电分析方法。在 p H 4.0 0的磷酸盐缓冲溶液中 ,镉、汞在钠型蒙脱石修饰玻碳电极上通过离子交换富集 ,获得一个灵敏的阳极溶出峰 ,由此可同时测定痕量的镉、汞离子。利用该方法测定镉、汞的线性范围分别为 8× 1 0 - 9到 2× 1 0 - 6 mol/L和 4× 1 0 - 8到 7.5× 1 0 - 6 mol/L ,检出限分别是1× 1 0 - 9mol/L和 8× 1 0 - 9mol/L。该方法简便、快速 ,灵敏度高。用此修饰电极测定了水样中的镉、汞离子 ,结果令人满意