Determination of Ni and Co using 2-quinolinethiol by adsorptive voltammetry

Summary A new method for the simultaneous determination of cobalt and nickel has been developed by differential pulse adsorptive voltammetry using 2-quinolinethiol as chelate. A separation of the two peaks by 0.3 V was achieved, allowing the determination of the two metals in a wide range of concentrations. The influence of pH, nature of the supporting electrolytes, preconcentration time and applied potential was investigated. Pb, Cd, Fe, Zn and Cr do not interfere. The determination limits were 10^–8 mol/l for Co and 10^–9 mol/l for Ni. The method was applied to mussel tissues and wines.     

Differential pulse adsorptive stripping voltammetric determination of nickel and cobalt in high purity aluminium

A sensitive method for the simultaneous determination of trace amounts of nickel and cobalt in pure aluminium has been described using differential pulse adsorptive stripping voltammetry (DPASV) by adsorptive accumulation of the dimethyl glyoxime (DMG) complex on the hanging mercury drop electrode (HMDE). As supporting electrolyte 0.1 mol/l ammonia buffer, pH 9.0, containing ammonium citrate and 5×10^–4 mol/l DMG has been used. The determination limit obtained has been as low as 0.5 g/g for Ni and 0.2 g/g for Co (using about 100 mg sample) with a relative standard deviation of 13% and 22%, respectively.     

Application of catalytic adsorptive stripping voltammetry of the cobalt-alpha-benzil dioxime complex to analysis of cobalt traces in metallic zinc

The catalytic adsorptive stripping voltammetric method with alpha-benzil dioxime and nitrite affords numerous advantages in cobalt determination. The detailed conditions of the determination of the cobalt traces in metallic zinc by catalytic adsorptive stripping voltammetry have been investigated. Both the linear sweep and the differential pulse stripping modes can be used with similar sensitivity. Possible interferences by Mn, Pb, Cu, Ni and Fe are evaluated. In the presence of 5 x 10(5) fold excess of Zn the linear dependence of the cobalt CASV peak current on concentration ranged from 0.05 mug/l to 3 mug/l. Optimal conditions include the accumulation potential of -0.65 V and the accumulation time of 10 sec. The results of the determination of 10(-5)% level of Co in the metallic zinc showed good reproducibility (relative standard deviation, RSD = 0.07) and reliability.     

Present potential of electrochemical methods for metal determinations in reference materials

Summary Based on high-pressure ashing, the potential to determine some trace metals (Zn, Cd, Pb, Cu, Ni, Co, Al, Tl, Cr, Fe) by anodic or cathodic stripping voltammetry in the square wave (SWV) and differential pulse modes (DPASV) is described. In comparison to the differential pulse mode, the square wave mode shows advantages for cathodic stripping and for zinc determination.New developments by use of potentiometric stripping analysis (PSA) permit the determination of Pb and Cd in whole blood without sample pretreatment and Pb, Cd, and Cu in milk and milk powder with simple pretreatment.Mercury film microelectrodes prepared by electrodeposition of Hg onto a carbon fiber were used for the rapid multicomponent trace determination of heavy metals in very small (5 l) samples by voltammetry and potentiometry.

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Gegenwärtiges Potential elektrochemischer Methoden für Metallbestimmungen in Referenzmaterialien

     

Simultaneous determination of Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe in water samples by differential pulse stripping voltammetry at a hanging mercury drop electrode

A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCI solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH3/NH4Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 x 10(-4) M). Finally, 1 x 10(-5) M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 x 10(-10) to 1.05 x 10(-9)M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.     

Cloud point extraction, preconcentration and simultaneous spectrophotometric determination of nickel and cobalt in water samples

Cloud point extraction has been used for the preconcentration and simultaneous spectrophotometric determination of nickel and cobalt after the formation of a complex with 2-amino-cyclopentene-1-dithiocarboxylic acid (ACDA), and latter analysis by spectrophotometer using Triton X-114 as surfactant. The parameters affecting the separation phase and detection process were optimized. Under the optimum experimental conditions (i.e. pH=5, 0.07 mM ACDA, Triton X-114=0.25% (w/v)), calibration graphs were linear in the range of 20-500 and 20-200 microg l(-1) with detection limits of 10 and 7.5 microg l(-1) for Ni and Co, respectively. The method was applied to the determination of Ni and Co in natural and waste water samples with satisfactory results.     

Differential pulse stripping voltammetry for the determination of nickel and cobalt in simulated PWR coolant

The determination of ionic nickel and cobalt in simulated PWR coolant at concentrations below 1 microg/l. by differential pulse stripping voltammetry at a hanging mercury-drop electrode has been investigated. The high sensitivity for these ions results from the adsorptive accumulation of their dimethylglyoximate complexes on the mercury drop. Boric acid does not interfere and if the samples are adjusted to pH 9 with an ammonia-ammonium chloride buffer, both nickel and cobalt can be determined in the same run. The relative standard deviations at concentrations below 2 microg/l. are of the order of 5-7% and the limits of detection for nickel and cobalt are about 8 and 2 ng/l. respectively. These performance statistics show that this method is the most sensitive method currently available for determination of soluble nickel and cobalt in PWR coolant and it should prove to be most valuable in any corrosion studies of the materials of construction of the primary circuit of a PWR.     

Synthesis,characterization and electrochemistry of a new organosoluble metal-free and metallophthalocyanines

4-[2-(Phenylthio)ethoxy]phthalonitrile 3 was synthesized by nucleophilic displacement of nitro group in 4-nitrophthalonitrile with 2-(phenylthio)ethanol 1. The metal-free phthalocyanine 4 was prepared by the reaction of a dinitrile monomer with 2-(dimethylamino)ethanol. Ni(II), Co(II), Cu(I) phthalocyanines 5, 7, 8 were prepared by reaction of the dinitrile compound with the chlorides of Ni(II), Co(II), Cu(I) in DMAE. Zn(II) phthalocyanine 6, was prepared by reaction of the dinitrile compound with the acetates of Zn(II) in DMAE. Electrochemical behaviours of novel metal-free, Co(II) and Zn(II) phthalocyanines were investigated by cyclic voltammetry, potential differential pulse voltammetry techniques. The new compounds were characterized by a combination of IR, ¹H NMR, ¹³C NMR, UV–Vis, elemental analysis and MS spectral data.     

Inversvoltammetrische Bestimmung von Schwermetallen in Fleisch, Leber und Nieren von Schlachtrindern

Zusammenfassung Die wesentlichen Aspekte einer leistungsstarken Analysenmethode zur Bestimmung der Schwermetallgehalte werden dargelegt. Im Anschluß an einen Naßaufschluß mit HNO₃/HClO₄ (2:1) der gefriergetrockneten Proben werden simultan Cu, Pb, Cd und Zn mit differentieller Pulsinversvoltammetrie und Ni und Co nach adsorptiver Voranreicherung ihrer Dimethylglyoximkomplexe mit differentieller Adsorptionspulsvoltammetrie bestimmt. Eine detaillierte Untersuchung von Kälbern, Ochsen und Kühen zeigt, daß mit Ausnahme der Speicherorgane Leber und Nieren, die Schwermetallgehalte im Fleisch sehr niedrig sind, so daß ein nennenswerter Beitrag zur Schwermetallaufnahme mit der menschlichen Nahrung durch Fleisch in der Regel nicht erfolgt.

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Voltammetric determination of heavy metals in the meat and organs of cattle

Summary The essentials of a new high-performance analytical procedure for the determination of heavy metal contents are presented. After appropriate sampling and wet digestion with HNO₃/HClO₄ (21) of freeze-dried samples (0.5 g) Cu, Pb, Cd and Zn are determined simultaneously by differential pulse anodic stripping voltammetry (DPASV) and Ni and Co after adsorption accumulation of their dimethylglyoxime complexes by adsorption differential pulse voltammetry (ADPV). The results of a detailed investigation of meat and organs from calfs, bulls and cows show that, except the storage organs liver and kidney, the heavy metal levels in meat are very low. Consequently, the contributions by meat to the heavy metal uptake of man with food remain unsignificant.

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Herrn Prof. Dr. W. Fresenius zum 70. Geburtstag gewidmet     

Evaluations of solid electrodes for use in voltammetric monitoring of heavy metals in samples from metallurgical nickel industry

Evaluation of different solid electrode systems for detection of zinc, lead, cobalt, and nickel in process water from metallurgical nickel industry with use of differential pulse stripping voltammetry has been performed. Zinc was detected by differential pulse anodic stripping voltammetry (DPASV) on a dental amalgam electrode as intermetallic Ni–Zn compound after dilution in ammonium buffer solution. The intermetallic compound was observed at –375 mV, and a linear response was found in the range 0.2–1.2 mg L^–1 (r²=0.98) for 60 s deposition time. Simultaneous detection of nickel and cobalt in the low g L^–1 range was successfully performed by use of adsorptive cathodic stripping voltammetry (AdCSV) of dimethylglyoxime complexes on a silver–bismuth alloy electrode, and a good correlation was found with corresponding AAS results (r²=0.999 for nickel and 0.965 for cobalt). Analyses of lead in the g L^–1 range in nickel-plating solution were performed with good sensitivity and stability by DPASV, using a working electrode of silver together with a glassy carbon counter electrode in samples diluted 1:3 with distilled water and acidified with H₂SO₄ to pH 2. A new commercial automatic at-line system was tested, and the results were found to be in agreement with an older mercury drop system. The stability of the solid electrode systems was found to be from one to several days without any maintenance needed.     

Simultaneous Determination of Seven Toxic Trace and/or Ultratrace Metals in Environmental Plants by Differential Pulse Voltammetry Without Change of Solution and Electrode

Abstract

A simple and reliable procedure simultaneously to determine seven trace and/or ultratrace toxic metals in a single sample of environmental plants has been presented. The procedure is based on the simultaneous determination of Cu, Pb and Cd by differential pulse anodic stripping voltammetry, of Zn and Mn by differential pulse voltammetry and of Ni and Co by differential pulse adsorption voltammetry at the hanging mercury drop electrode. The details of sampling, washing and drying of samples and the approach of digestion and preparation of samples for voltammetric determination have been investigated. The method has been applied to determination of the seven metals in grass and hucerne from different environments.     

Neutron activation analysis of high purity nickel by solvent extraction using 2-benzylpyridin/benzene

A radiochemical neutron activation analysis using solvent extraction has been applied for the determination of trace impurities in high purity nickel. Because of the high activity of⁵⁸Co produced by the nuclear reaction,⁵⁸Ni(n,p)⁵⁸Co, cobalt should be separated from the impurities. Removal of cobalt from the other trace elements in the aqueous acidic solution containing 1M thiocyanate ion (KSCN) was achieved by extraction with 1M2-benzylpyridin (BPy) in benzene. From the result of tracer experiments, cobalt was completely separated from most other elements except Fe, Mo and Zn. To determine the experimental accuracy, NIST SRM 673 nickel oxide was analyzed and the results agreed well within 10% deviation. This established radiochemical method was applied to the analysis of high purity nickel samples.     

Determination of cobalt by catalytic-adsorptive differential pulse voltammetry

A novel method is described for the determination of cobalt(II) by differential pulse voltammetry, based on accumulation of a cobalt complex, [CoSCNNO]⁺, on a hanging mercury drop electrode, followed by measurement of the catalytic current of the adsorbed complex. The effects of various experimental parameters on the catalytic current were investigated. The current was found to be linear for 0.3 nM to 100 nM Co, with a detection limit of 70 pM (4.1 ng l⁻¹) and a relative standard deviation of 1.6% for 50 nM Co (n = 25). The developed method showed considerable selectivity against nickel and zinc. A possible mechanism of the reduction process is proposed.     

Determination of manganese,iron, cobalt and nickel in air and water by atomic absorption spectroscopy

Flames of 4 different kinds and of various compositions were studied for their suitability for atomic absorption spectroscopy for the determination of manganese, iron, cobalt and nickel. The effects of various other factors such as lamp current, slit-width and position of the burner were also investigated. Interference effects of a large number of ions and compounds were studied. Very few ions were found to interfere and means of eliminating the interferences noted are described. As a result of the investigation, sensitive and selective procedures for the determination of manganese, iron, cobalt and nickel are reported. Sensitivities are Mn, 0.01 mg/l; Fe, 0.05 mg/l; Co, 0.03 mg/l and Ni, 0.02 mg/l for 1% absorption.     

A reliable and ultrasensitive voltammetric method for the determination of molybdenum

Summary The determination of molybdenum(VI) in aquatic media by polarography, voltammetry and adsorptive stripping voltammetry using the formation of a Mo-chlorate-mandalic acid complex at +100 mV (SCE) is described. The 3 s_blank-detection limit is 0.1 nmol/l with differential pulse adsorptive stripping voltammetry (DPAdsSV, catalytic current). The calibration graphs are linear up to 200 nmol/l for the latter, 400 nmol/l for staircase voltammetry without accumulation time and 1 mg/l for staircase polarography. The accuracy of the DPAdsSV method was checked by analysis of a standard reference water material. The utility of differential pulse voltammetry was tested in different aquatic media, e.g., tap water, ground water, surface water.

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Eine zuverlässige und äußerst empfindliche Methode zur Bestimmung von Molybdän

     

Simultaneous Trace Determination of Nickel and Cobalt in Natural Waters by Differential Pulse Polarography

Abstract

A differential pulse polarographic method has been developed for the simultaneous low level determination of nickel and cobalt in the presence of furildioxime in natural waters. The nature of the electrode processes was studied with cyclic voltammetry. Limits of determination of 0.4 μg/L and 0.15 μg/L were achieved for nickel and cobalt respectively     

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.     

Direct and simultaneous voltammetric analysis of heavy metals in tap water samples at Assiut city: an approach to improve the analysis time for nickel and cobalt determination at mercury film electrode

Tap water samples (Assiut city, lie in the middle north of upper Egypt, approx. 370 km from Cairo, January-March, 2002) were taken from the eight sampling sites of different locations at Assiut city. The samples are analyzed to determine the total content of cadmium, copper, lead and zinc by differential pulse anodic stripping voltammetry (DPASV) while nickel and cobalt are determined by a new simple differential pulse adsorptive stripping voltammetry (DPAdSV), using dimethylglyoxime (DMG) as the complexing agent. This method uses sodium sulfite as the supporting electrolyte, which facilitates the removal of oxygen interference without the traditional necessity of purging with inert gas. The effect of various parameters was studied using DPASV (for Cd, Pb, Cu and Zn) and AdSV (for Ni and Co) methods. Subsequently, under the so found experimental conditions, the stability of calibration curves and the detection limits (μg/l) have been determined. The data achieved (for all metals utility) are comparable to those measured by the graphite furnace atomic absorption spectrophotometric (GF-AAS) method. The effects of the interferences between these metal ions have been investigated. Moreover, the effect of storage was discussed and the obtained results were compared favorably with standard official methods. Statistical analysis of the database exhibits applicability and the accuracy of the techniques. The results obtained from the two techniques (Voltammetry and GF-AAS) are in very good agreements in the most tap water samples.     

Extraction-polarographic determination of cobalt(II) and nickel(II) as 2,2′-bipyridine complexes in acetonitrile

The tris(2,2′-bipyridine)cobalt(II) complex gives a reversible d.c. wave with E$\text{1}\text{2}$ = ?1.02 V vs. SCE and a sharp differential pulse peak at E_p = ?1.03 V in a salted-out acetonitrile phase. A simple selective method is described for the determination of cobalt(II); down to 0.25 μg of cobalt(II) can be determined in presence of large amounts of Ni, Zn, Cd, Pb, and Cu; iron(III) can be masked with sodium fluoride. The method is applicable to the determination of >0.0l% cobalt in nickel salts and >5 × 10^?5% cobalt in iron salts. Nickel(II) can also be extracted from aqueous solution and determined by differential pulse polarography, even in presence of a 20-fold amount of cobalt(II) by masking with EDTA; >0.01% of nickel in cobalt salts can be determined reproducibly.     

Preconcentration of trace heavy metals in water by coprecipitation with magnesium oxinate for electrothermal atomic absorption spectrometry

Nanogram quantities of heavy metals in 200 ml of water were quantitatively preconcentrated by coprecipitation with magnesium oxinate at pH 9–9.5. The precipitate was collected on a 1-m Nuclepore membrane filter and then dissolved in 5 ml of 1 mol/l nitric acid. After diluting to 10 ml with water, a 10- or 20-l aliquot of the solution was directly analyzed by electrothermal atomic absorption spectrometry using deuterium background correction. The background absorption due to the collector magnesium oxinate was negligibly small. The optimized coprecipitation technique has been applied to the determination of cobalt, nickel, copper, cadmium and lead at the ppt level in river and seawater. The relative standard deviations were within 10% and the detection limits were 0.025 (for Co), 0.019 (for Ni), 0.006 (for Cu), 0.001 (for Cd) and 0.017 g/l (for Pb). Blanks through the whole procedure were not detectable.