Highly Selective Adsorptive Cathodic Stripping Voltammetric Determination of Uranium in the Presence of Pyromellitic Acid

A very sensitive and selective adsorptive cathodic stripping procedure for trace measurement of uranium is presented. The method is based on adsorptive accumulation of the uranium‐pyromellitic acid (benzene‐1,2,4,5‐tetracarboxylic acid) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. Influences of effective parameters such as pH, concentration of pyromellitic acid, accumulation potential and accumulation time on the sensitivity were studied. The peak current was proportional to the concentration of U(IV) up to 40 ng mL^?1 with a limit of detection of 0.136 ng mL^?1 with an accumulation time of 120 s. The range of linearity enhanced to 71.4 ng mL^?1and the detection limit improved to 0.058 ng mL^?1with accumulation times of 60 s and 300 s respectively. The relative standard deviation for 10 replicate determination of 4.76 ng mL^?1 U(IV) was equal to 2.7%. The possible interference by major cations and anions are investigated. The method was applied to the determination of uranium in some analytical grade salts, seawater and in synthetic samples corresponding to some uranium alloys with satisfactory results.     

Trace Determination of Chromium by Square‐Wave Adsorptive Stripping Voltammetry on Bismuth Film Electrodes

This works reports the use of adsorptive stripping voltammetry (AdSV) for the trace determination of chromium on a rotating‐disk bismuth‐film electrode (BFE). During the reductive accumulation step, all the chromium species in the sample were reduced to Cr(III) which was complexed with cupferron and the complex was accumulated by adsorption on the surface of a preplated BFE. The stripping step was carried out by using a square‐wave (SW) potential‐time voltammetric signal. Electrochemical cleaning of the bismuth film was employed, enabling the same bismuth film to be used for a series of measurements in the presence of dissolved oxygen. The experimental variables as well as potential interferences were investigated and the figures of merit of the method were established. Using the selected conditions, the 3σ limit of detection for chromium was 100 ng L^?1 (for 120 s of preconcentration) and the relative standard deviation was 3.6% at the 2 μg L^?1 level (n=8). Finally, the method was applied to the determination of chromium in real samples with satisfactory results.     

Cathodic and Adsorptive Stripping Votammetry of Naftazone

Abstract

Naftazone (1,2-naphthoquinone-2-semicarbazone) undergoes a reversible two-electron transfer in both acidic and alkaline solutions and also gives rise at pH > 7 to an anodic wave attributed to the formation of a mercury derivative. Cathodic stripping voltammetry is proposed to determine the compound down to 5 × 10^?9 M after accumulation of its mercury salt formed at -0.05V in a 0.05M sodium hydroxide solution. These results have been compared with those obtained by performing an adsorptive collection of the drug in a pH 3 sodium perchlorate solution. Concentrations ranging from 1 × 10^?7 to 2 × 10^?7M can be easily investigated, the detection limit being 7 × 10^?11M. The influence of several operational parameters has also been considered.     

Determination of Folic Acid at a Bismuth Film Electrode by Adsorptive Stripping Voltammetry

This article reports a new simple and sensitive method for the determination of folic acid by adsorptive stripping voltammetry. The method is based on the accumulation of folic acid at a bismuth film plated in situ on a glassy carbon substrate. In order to stabilize bismuth ions, sodium potassium tartrate was added to the supporting electrolyte. The bismuth film formation and folic acid accumulation conditions were optimized and measurements were carried without solution deaeration. The calibration graph was linear from 5 × 10^?10 to 2 × 10^?8 mole per liter with an accumulation time of 180 seconds with a limit of detection of 2 × 10^?10 mole per liter. The relative standard deviation for 5 × 10^?9 mole per liter of folic acid was 3.1 percent (n = 5). The method was successfully applied for determination of folic acid in pharmaceutical preparations.     

Determination of Aluminum by Adsorptive Cathodic Stripping Voltammetry with 1,2‐Dihydroxyanthraquinone‐3‐Sulfonic Acid (DASA): Effect of Thin Mercury Film Electrode

An analytical technique for aluminum (Al) based upon the complexation reaction between Al and the ligand – DASA (1,2‐dihydroxy‐anthraquinone‐3‐sulfonic acid) has previously been implemented successfully at the hanging mercury drop electrode (HMDE). There are several advantages of using mercury film electrodes (TMFE) over the HMDE, particularly if disposal of mercury is of concern. The novelty of using TMFE for adsorptive cathodic stripping voltammetry (ACSV) of Al – DASA is demonstrated in this paper. The peak potential used for the detection of Al in this system was at ?1.15 V (vs. Ag/AgCl). The method produced a limit of detection (LOD) of 1 μM (n=5) and a linear working range of 1–20 μM Al. Atomic force microscopy methods were used to investigate the nature of the TMFE and its interaction with DASA. The mercury droplets on the TMFE have a limited volume and this may lead to overloading of the electrode at relatively low concentrations of DASA. Interferences from Fe, Ca, Zn and Mg were investigated with only Fe appearing to interfere with the Al‐DASA system. Two masking agents (o‐phenanthroline and 2,2′‐bipyridyl) were shown to be effective at preventing the Fe interference.     

邻苯三酚红修饰碳糊电极吸附伏安法测定痕量铋

报道了采用邻苯三酚红修饰碳糊电极测定痕量铋的方法。在０．３０ｍｏｌ／Ｌ的ＨＣｌ溶液中,于－０．１０Ｖ搅拌富集３ｍｉｎ,然后在－０．３５Ｖ静止还原６０ｓ,再进行阳极化扫描,在－０．１０Ｖ左右获得灵敏的铋溶出峰,二次导数民流与铋浓度在１．０＊１０＾－９－６．０＊１０＾－７ｍｏｌ／Ｌ范围内呈线性关系,同限为５＊１０＾－１０ｍｏｌ／Ｌ。对电极反应机理进行了讨论。     

Adsorptive Cathodic Stripping Voltammetry for Quantification of Alprazolam

A simple and highly sensitive electrochemical sensor was developed for adsorptive cathodic stripping voltammetry of alprazolam. Based on an electrochemically pretreated glassy carbon electrode, the sensor demonstrated good adsorption and electrochemical reduction of alprazolam. The morphology of the glassy carbon electrode and the electrochemically pretreated glassy carbon electrode were characterized by scanning electron microscopy/energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The electrochemical behaviors of alprazolam were determined by cyclic voltammetry, and the analytical measurements were studied by adsorptive cathodic stripping voltammetry. Optimized operational conditions included the concentration and deposition time of sulfuric acid in the electrochemical pretreatment, preconcentration potential, and preconcentration time. Under optimal conditions, the developed alprazolam sensor displayed a quantification limit of 0.1 mg L⁻¹, a detection limit of 0.03 mg L⁻¹, a sensitivity of 67 µA mg⁻¹ L cm⁻² and two linear ranges: 0.1 to 4 and 4 to 20 mg L⁻¹. Sensor selectivity was excellent, and repeatability (%RSD < 4.24%) and recovery (82.0 ± 0.2 to 109.0 ± 0.3%) were good. The results of determining alprazolam in beverages with the developed system were in good agreement with results from the gas chromatography–mass spectrometric method.     

Voltammetric Behavior of Testosterone on Bismuth Film Electrode: Highly Sensitive Determination in Pharmaceuticals and Human Urine by Square‐Wave Adsorptive Stripping Voltammetry

In this paper, an electrochemical application of bismuth‐film electrode (BiFE) fabricated via ex‐situ electrodeposition onto a glassy carbon electrode for testosterone determination was investigated in aqueous and aqueous/surfactant solutions. In cyclic voltammetry, the compound showed one irreversible and adsorption‐controlled reduction peak. The BiFE revealed good linear response in the examined concentration range of 1 to 45 nmol L^?1 testosterone in Britton? Robinson buffer, pH 5.0 containing 3 mmol L^?1 cetyltrimethylammonium bromide. The limit of detection was 0.3 nmol L^?1 (0.09 ng mL^?1). Finally, the BiFE was satisfactorily applied for quantitation of testosterone in both pharmaceutical (oil‐based ampoule) and biological (human urine) samples.     

铋膜电极方波吸附溶出伏安法测定纺织品中痕量钴和镍

本文建立了在铋膜修饰电极上采用方波吸附溶出伏安法同时测定纺织品中痕量Co2+和Ni2+的方法.以NH3-NH4Cl作为缓冲液,在丁二酮肟浓度为10 μmol/L的体系中,Co2和Ni2+的还原峰电位分别为-1.13 V和-1.03 V.当缓冲溶液pH为9.2,富集电位为-0.7V,富集时间为200 s时,C02 +和Ni2+在0.5～50 μg/L范围呈现良好的线性关系,相关系数R2＞0.99,其检出限分别为0.79 μg/L和0.96 μg/L,其它金属离子的干扰较小.采用标准加入法测定纺织品中Co>和Ni2+,回收率在94.88％～104.14％之间.     

Determination of Melatonin Hormone in Bulk Form,Tablets and Human Serum by Square‐Wave Cathodic Adsorptive Stripping Voltammetry

Melatonin hormone plays an important role in many distinct physiological functions. A fully validated, sensitive and reproducible square‐wave cathodic adsorptive stripping voltammetric procedure was described for determination of melatonin in bulk form, tablets and human serum. The procedure was based on the reduction of the adsorptive hormone onto a hanging mercury drop electrode. Reduction behavior of melatonin was studied in both Britton‐Robinson (pH 2–11) and acetate (4.5–5.5) buffers. Acetate buffer of pH 5.0 was found reasonable as a supporting electrolyte for assay of the drug. The square‐wave cathodic adsorptive stripping voltammogram of melatonin showed a single well‐defined peak at ?1.45 V (vs. Ag/AgCl/KCl_s) using an accumulation potential of ?0.65 V. This peak may be attributed to the reduction of C?O double bond of the amide functional group of the reactant molecule. A mean recovery for 1×10^?8 M melatonin in bulk form followed 30 s accumulation of 98.87%±0.78 and a detection limit of 3.13×10^?10 M were achieved. The proposed procedure was successfully applied for the determination of the drug in tablets and human serum with mean recoveries of 97.68%±0.57 and 101.67%±0.85, respectively. A detection limit of 8.80×10^?10 M was achieved for the determination of the drug in human serum. Results of the proposed method were comparable and coincided with those obtained by reported method. Vitamin B₆ and common excipients, which are co‐formulated with melatonin, did not interfere. Also the effect of some interfering compounds such as serotonin, tryptophan and 5‐hydroxytryptophan on the determination of melatonin in human serum was studied, and all have no significant effect on the assay recovery.     

Simultaneous Determination of Tyrosine and Histidine by Differential Pulse Cathodic Stripping Voltammetry Using H‐point Standard Addition Method in Tap and Seawater

H‐point standard addition method (HPSAM) has been applied for simultaneous determination of tyrosine and histidine in trace levels using copper ions by adsorptive cathodic stripping voltammetry. The amino acids‐Cu(II) complexes were accumulated onto the surface of a hanging mercury drop electrode for 40 s. The reduction peaks of preconcentrated complexes were used for simultaneous determination of amino acids in the range 8.0–180 and 30–1100 nM for tyrosine and histidine respectively. The effect of various parameters such as pH, concentration of copper, accumulation time and scan rate on the selectivity were studied. Under the optimized conditions the method was successfully applied for determination of tyrosine and histidine in synthetic and real samples.     

Determination of Atrazine in Natural Water Samples by Differential Pulse Adsorptive Stripping Voltammetry Using a Bismuth Film Electrode

A new method using differential pulse adsorptive stripping voltammetry for the determination of atrazine (ATZ) in natural water samples using a bismuth film electrode (BiFE) is proposed. The calibration curve was linear in the atrazine concentration range from 6.7×10^?7 to 2.0×10^?5 mol L^?1, with a limit of detection (LOD) of 1.4×10^?7 mol L^?1. The proposed electrode was applied for atrazine determination with satisfactory results compared with a high‐performance liquid chromatography method (HPLC).     

Adsorptive Cathodic Stripping Voltammetry Determination of Ultra Trace of Lead in Different Real Samples

Abstract

In the present work, an adsorptive cathodic stripping voltammetric method using a hanging mercury drop electrode (HMDE) was described in order to determine the ultra trace of lead ions with carbidopa in different real samples. The method is based on accumulation of lead metal ion on mercury electrode using carbidopa as a suitable complexing agent. The potential was scanned to the negative direction and the differential pulse stripping voltammograms were recorded. The instrumental and chemical parameters were optimized. The optimized conditions were obtained in pH of 8.4, carbidopa amount of 1.0×10^?6 M, accumulation potential of 0. 0 V, accumulation time of 100 s, scan rate of 100 mV/s and pulse height of 50 mV. The relationship between the peak current versus concentration was linear over the range of 2.4×10^?10–4.8×10^?7 M. The limits of detection were 5.8×10^?11 M and the relative standard deviation at 4.8×10^?10, 2.1×10^?8, and 2.4×10^?7 M of lead ion were obtained 3.2, 2.9, and 2.7%, respectively (n=7).     

Cathodic Stripping Voltammetry of Uracil. Experimental and Theoretical Study Under Conditions of Square‐Wave Voltammetry

The electrode mechanism of uracil at a hanging mercury drop electrode (HMDE) is studied under cathodic stripping square‐wave voltammetric mode owing to the cathodic dissolution of a sparingly soluble compound formed between the electrode material and uracil. The experimental results can be partly explained in the light of the recent theory for cathodic stripping processes of insoluble salts under conditions of square‐wave voltammetry. It is established that the electrode reaction is complicated by attractive interactions between the deposited species of the insoluble compound. To elucidate the electrode mechanism completely a novel theoretical model is developed considering adsorption of the reacting analyte and lateral interactions between species of the insoluble compound. With the help of numerical simulations the effect of interactions is studied in detail, emphasizing the properties of the response that can be used as diagnostic criteria for recognition of the type of interaction forces. Theoretically predicted voltammetric properties agree well with the experimental results enabling clarification of the complex electrode mechanism of uracil at HMDE.     

Catalytic Adsorptive Stripping Voltammetry of Germanium(IV) in the Presence of Gallic Acid and Vanadium(IV)‐EDTA

A highly sensitive and selective catalytic adsorptive cathodic striping procedure for the determination of trace germanium is presented. The method is based on adsorptive accumulation of the Ge(IV)‐gallic acid (GA) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species. The reduction current is enhanced catalytically by addition of vanadium(IV)‐EDTA. The optimal experimental conditions include the use of 0.03 mol/L HClO₄ (pH1.6), 6.0×10^?3 mol/L GA, 3.0×10^?3 mol/L V(IV), 4.0×10^?3 mol/L EDTA, an accumulation potential of ?0.10 V(vs. Ag/AgCl), an accumulation time of 120 s and a differential pulse potential scan mode. The peak current is proportional to the concentration of Ge(IV) over the range of 3.0×10^?11 to 1.0×10^?8 mol/L and the detection limit is 2×10^?11 mol/L for a 120 s adsorption time. The relative standard deviation at 5.0×10^?10 mol/L level is 3.1%. No serious interferences were found. The method was applied to the determination of germanium in ore, mineral water and vegetable samples with satisfactory results.     

Square-Wave Cathodic Stripping Voltammetry of Marcellomycine. A Sensitive Analytical Method

Abstract

Square-wave adsorptive stripping voltammetry has been applied to the determination of a new cytostatic anthracyclinic compound, marcellomycine. 100-fold and 1000-fold increases of sensitivity have been found with regard to the differential pulse stripping voltammetry and differential pulse polarography respectively. The detection limit is fixed at 5 × 10^?9 M.     

Nafion—玻碳修饰电极阴极溶出伏安法测定痕量铋的研究

研究并提出在HNO_3-NaCl-硫脲(Tu)体系中,Nafion/玻碳(Gc)修饰电极阴极溶出伏安法测定痕量鉍的方法。表明Tu具络合协同作用,使Nation阳离子交换能力提高。本法检出限为5×10~(-9)mol/L Bi~(3+)(td:5min),电极表面易于再生,文中研究了电极过程机理,计算得[Bi(Tu)_6]~(3+)在Nafion膜中的分配系数(K_D),扩散系数(D)和选择性系数(K_H~[Bi(Tu)_6~+]~(3+))分别为7.57×10~5,5.9×10~(-11)cm~2/s及3.39。     

Chemical Speciation of Antimony(III and V) in Water by Adsorptive Cathodic Stripping Voltammetry Using the 4‐(2‐Thiazolylazo) – Resorcinol

A simple adsorptive cathodic stripping voltammetry method has been developed for antimony (III and V) speciation using 4‐(2‐thiazolylazo) – resorcinol (TAR). The methodology involves controlled preconcentration at pH 5, during which antimony(III) – TAR complex is adsorbed onto a hanging mercury drop electrode followed by measuring the cathodic peak current (I_p,c) at ?0.39 V versus Ag/AgCl electrode. The plot of I_p,c versus antimony(III) concentration was linear in the range 1.35×10^?9–9.53×10^?8 mol L^?1.The LOD and LOQ for Sb(III) were found 4.06×10^?10 and 1.35×10^?9 mol L^?1, respectively. Antimony(V) species after reduction to antimony(III) with Na₂SO₃ were also determined. Analysis of antimony in environment water samples was applied satisfactorily.     

吸附溶出催化伏安法测定人参中的锗

本文提出了利用吸附溶出催化伏安法测定人参中锗的方法。最佳体系为:2.5×10~(-2)mol/LH_2O_2、2.0×10~(-2)mol/L邻苯二酚、2.0×10~(-3)mol/L H_2SO_4。线性范围为2.0×10~(-9)～2.0×10~(-7)mol/L。当富集时间为4 min时,最低检测浓度为4.0×10~(-10)mol/L。此法己成功地应用于测定人参中的锗。     

Stripping Voltammetry with Bismuth Modified Graphite‐Epoxy Composite Electrodes

The attractive performance of graphite‐epoxy composite electrodes (GECE) surface‐modified with a bismuth film (Bi‐GECE) for simultaneous and separate stripping determination of trace amounts of heavy metals (lead, cadmium and zinc) is described. Several key parameters have been optimized. Bi‐GECEi electrode shows superior accumulation properties when compared to bare GECE or even to Hg‐GECE. Bi‐GECE exhibits well‐defined, undistorted, reproducible and sharp stripping signals with RSD of 2.99%, 1.56% and 2.19% for lead, cadmium and zinc respectively. Detection limits of 23.1, 2.2 and 600 μg/L for lead, cadmium and zinc were obtained. Sharp peaks with high resolution (of neighboring signals) that permit convenient multi‐elemental measurements resulted. The applicability of the electrodes to the real samples (tap water and soil sample) was also tested and promising results with good recoveries were obtained.