Determination of copper in seawater by anodic stripping voltammetry

Copper in surface seawater has been determined using both hanging mercury drop and thin film electrodes. Total copper was found to be in the range 0.4–0.7 μg l^?1, and labile copper in the range 0.2–0.4 μg l^?1. Most of the copper present in seawater is complexed with or adsorbed on organic matter, and a smaller percentage is associated with inorganic colloids. Seawater contains both organic and inorganic compounds which will react with approximately 1×10^?8M added ionic copper. Because of the presence of the complexing agents, peak current-copper concentration calibration curves in seawater are non-linear, and care must be exercised in using spiked results in the calculation of the copper content. The thin film electrode (TFE) is more suitable than the hanging mercury drop electrode for determining copper in seawater, although the TFE results are more dependent on deposition potential, and suffer from interference by nickel if very negative deposition potentials are used.     

Determination of traces of bismuth in copper by anodic stripping voltammetry

Summary Procedures are described for the determination of bismuth impurities in. copper using anodic stripping voltammetry on a hanging mercury drop electrode. Bismuth was previously separated from copper by cation or anion exchange in hydrochloric acid. The method was applied to the analysis of commercially available high purity copper, showing satisfactory sensitivity and accuracy. The detection limit was about 2×10^–9 M bismuth in solution for a pre-electrolysis time of 15 min (–0.5 V vs. Ag/AgCl); this corresponds to 0.004 ppm of bismuth for a 1 g sample and a final volume of 10 ml after separation.

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Bestimmung von Wismutspuren in Kupfer durch anodische Amalgamvoltammetrie

Zusammenfassung Mit hängendem Quecksilbertropfen. Wismut wird vor der Bestimmung durch Kationen oder Anionenaustausch aus salzsaurer Lösung vom Kupfer abgetrennt. Das Verfahren wurde zur Analyse von handelsüblichem hochreinem Kupfer angewendet. Mit einer Vorelektrolysedauer von 15 min (–0,5 V gegen Ag/AgCl) konnten noch 2×10^–9 M Bi bestimmt werden; das entspricht 0,004 ppm Bi für eine 1 g-Probe bei einem Endvolumen von 10 ml nach der Trennung.

     

Determination of copper and lead in schist by anodic stripping voltammetry

Samples were decomposed in HClO₄/HF mixture in a Teflon beaker to avoid electrochemical interference from platinum ions. The residue remaining after evaporation to dryness was taken up in nitric acid and examined by anodic stripping voltammetry. Both the hanging mercury drop electrode and the rotating glassy carbon electrode, mercury-plated in situ, were used with success. Copper at 120 ppm and lead at 40 ppm were determined with a relative standard deviation of 6%. The schist was the Nordic reference sample ASK-2.     

Determination of total copper in haemodialysis water by differential-pulse anodic stripping voltammetry

An anodic stripping voltammetric method was developed in order to determine copper in the water used to prepare haemodialysis solutions. The interference from organic matter was overcome by high-pressure bomb mineralization. The electrochemical results were compared with those obtained by using graphite furnace atomic absorption spectrometry and the correlation was excellent (r = 0.983, p < 0.001). The detection limit was 0.2 μg l^?1 copper.     

Differential-pulse anodic stripping voltammetry of copper with a chemically-modified glassy carbon electrode

Copper at the low or fractional ng g^?1 level in 0.1 M oxalic acid solutions at pH 1.6 is electrodeposited on a chemically-modified glassy carbon electrode with surface-bound

groups at ?0.6 V vs. Ag/AgCl (3.3 M KCl). The deposit is then anodically stripped in the same solution, a current-potential curve being recorded by the differential-pulse technique. The advantages of this electrode over an unmodified glassy carbon electrode include higher sensitivity, precision and selectivity; the modified electrode can be used 50–100 times without further treatment.     

Trace analysis by anodic stripping voltammetry

Summary An anodic stripping voltammetric method for the determination of zinc in silicates is described and discussed. The method is sensitive and is not affected by interferences resulting from varying sample composition.

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Zusammenfassung Ein Verfahren zur Bestimmung von Zink in Silicaten mit Hilfe der anodischen Amalgamvoltammetrie wird beschrieben und diskutiert. Das Verfahren ist empfindlich und wird durch verschiedenartige Zusammensetzung der Probe nicht beeinflußt.

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Dedicated to Prof. Dr. M. von Stackelberg on his 70th birthday.

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This work was performed under the sponsorship of the U.S.National Bureau of Standards. Reproduction of this article, with the customary credit to the source, is permitted.     

Cathodic stripping voltammetry of cysteine using silver and copper solid amalgam electrodes

Silver and copper solid amalgam electrodes (modified with mercury meniscus and based on amalgamation of fine metallic powder) have been successfully tested for cathodic stripping voltammetry of cysteine. In the case of the silver solid amalgam electrode AgSAE the relative standard deviation (RSD) and the detection limit (3 SD) reached +/-2.3% and 3x10(-9) mol l(-1) cysteine, respectively.     

Determination of traces of antimony and tin in copper by anodic stripping voltammetry

The determination of antimony and tin impurities in copper by anodic stripping voltammetry on a hanging mercury drop electrode is described. Antimony and tin were previously separated from copper by distillation with hydrobromic acid or a mixture of hydrobromic acid and hydrochloric acid. The method was applied to the analysis of various high-purity copper samples, commercially available, showing satisfactory sensitivity and precision. The determination limit was about 1.4· 10^-9M for antimony and 7·10^-10M for tin in solution, for pre-electrolysis times of respectively 15 and 25 min; this corresponds to 0.8 p.p.b. of antimony and 0.3 p.p.b. of tin for a 2-g sample and a final volume of 10 ml after separation.     

Elimination of iron interference in the differential pulse anodic stripping voltammetry of copper

The interference of iron(III) on the quantitation of copper(II) in citrate media by differential-pulse anodic stripping voltammetry can be completely removed by lowering the pH to 1.5 with 70% perchloric acid.     

Simultaneous determination of copper and lead in ethanol fuel by anodic stripping voltammetry

The presence of trace metals in car fuels plays an important role in the engine maintenance. In addition, these metals contribute for the environmental contamination in big cities and their control is necessary. Square Wave Stripping Voltammetry (SWSV) is a very sensitive technique for elemental trace determination and was applied for ethanol fuel analysis. The first studies were done searching for the best conditions for copper determination in alcoholic medium, utilizing gold electrodes. During these studies, the possibility of the simultaneous determination of copper and lead in the same experiment was observed. Two procedures for the analysis of these metals were adopted: The direct quantification of metals in alcohol–water mixtures and a second way that involves the evaporation of the organic solvent and re-suspension of the ions with water+electrolyte. Good recovery values were obtained for synthetic samples spiked with known amounts of metals. The results obtained for the two methods were in good agreement. The detection limits for copper and lead in 75% ethanol–water ratio solution were calculated as 120 and 235 ng l⁻¹, respectively, for 15-min deposition time.     

Determination of copper by anodic stripping voltammetry: anomalous behavior in sea water

Repeated cycles of plating and stripping using a mercury-coated graphite electrode in raw sea water show increasing negative errors for copper while lead and cadmium are unaffected. This phenomenon, which is not observed in acidified sea water, is attributed to formation of electroinactive Cu(I) species on the electrode.     

The determination of copper in silicon by anodic stripping and differential pulse voltammetry

A critical comparison of the application of differential pulse voltammetry and anodic stripping voltammetry to the determination of micro amounts of copper in silicon is described. The anodic stripping technique offers advantages when a dropping mercury capillary with a long drop time is used. The method recommended allows the determination of copper in silicon with a precision of ± 5 %; the limit of determination is about 1μg g^-1. Calibration graphs are linear in the range 0–0.2 μg Cu ml^-1. Methods for the dissolution of silicon are also compared.     

Intermetallic compounds and the determination of copper and zinc by anodic stripping voltammetry

The intermetallic CuZn compounds produced during the simultaneous deposition of copper and zinc at a preformed mercury film electrode were studied. Over a wide range of metal concentration ratios, the real concentrations of metals in the amalgam were calculated from the peak areas obtained by anodic stripping voltammetry. The results indicate the formation of CuZn (insoluble) and CuZn2 (soluble) compounds with K_so=5×10^?4 and β₂=100, respectively. The electrodeposition potential of ?0.85 V vs. SCE for the reduction of copper in presence of zinc is confirmed as correct.     

Interferences in the determination of copper in natural waters by anodic stripping voltammetry

Copper(I)-binding anions such as cyanide and thiocyanate, and polysaccharides, when present in non-saline waters are shown to produce an additional, more anodic wave during the determination of copper by stripping voltammetry. The origins of this wave and potential interferences in determinations of copper and copper-complexing capacities are discussed. The effect of inadequate oxygen removal is reported.     

Determination of traces of copper and silver in tantalum metal by anodic stripping voltammetry

Summary Nanogram quantities of copper and silver are electrodeposited on a glassy carbon electrode from a hydrofluoric-nitric acid solution containing 0.5–1 g of tantalum. The deposit is then anodically removed in 0.1M hydrochloric acid, a current-voltage curve being recorded. The impurities at the parts per billion level in high-purity tantalum metal powder are determined within 3 hours.

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Zusammenfassung Nanogrammengen Kupfer und Silber werden aus flußsaurer, salpetersaurer Lösung von 0,5–1 g Tantal elektrolytisch an einer Elektrode aus glasartigem Kohlenstoff abgeschieden. Während der anodischen Auflösung in Salzsäure wird eine Stromspannungskurve geschrieben. Verunreinigungen in der ppb-Größenordnung in hochreinem Tantalpulver lassen sich so innerhalb 3 Stunden bestimmen.

     

The determination of gold by anodic stripping voltammetry

A method is described for the routine determination of gold as its chloride or cyanide complex by anodic stripping voltammetry at a glassy carbon electrode coupled to a microprocessor-controlled voltammeter. The preferred supporting electrolyte is 0.1 M HCl/0.32 M HNO₃, with plating at ?200 mV or ?1200 mV (vs. Ag/AgCl). The stripping peak potentials range from 830 to 1150 mV (vs. Ag/AgCl) depending on concentration and plating time. Precision (percent relative standard deviation) is better than 5 % for a range of concentrations between 5 μg l^?1 and 1000 μg l^?1. The detection limit is about 5 μg l^?1 for a 5-min plating period. Interferences from Cu, Hg, Ag and other electroactive species are overcome by preliminary extraction with diethyl ether.     

Microcell for anodic stripping voltammetry of trace metals

A microcell for batch injection stripping voltammetry of trace metals with the use of a rotating disk working electrode has been developed and tested for samples of 0.2-0.3 mL. The detection limits for Pb(2+), Cd(2+) and Zn(2+) are 0.03 ppb and 0.3 for a deposition time of 5.0 and 0.5 min, respectively.     

Application of semidifferential electroanalysis to anodic stripping voltammetry

A new voltammetric technique, Semidifferential electroanalysis, in which the semiderivative, e, of the current, i, is measured as a function of electrode potential, has been applied for detection in anodic stripping voltammetry. The semiderivative of the current is defined by [fx131-1.tif] Cd²⁺, Pb²⁺, and Tl⁺ in 0.1 M KNO₃ at different pH values were tested as samples on a hanging mercury drop working electrode. Symmetrical sharp peaks were observed for the re-dissolution processes of metal amalgams formed during pre-electrolysis at -1.0 V vs. SCE. The peak potentials of e vs. E curves for the above three amalgams agreed well with the literature values for d.c. polarographic half-wave potentials. The peak heights were proportional to the pre-electrolysis time up to about 5 min, to the potential scan rate in the range 60–160 mV s^-1, and to the concentrations of Cd²⁺, Pb²⁺, and Tl⁺ in the original solution in the range 10^-6–10^-9 M. The relative standard deviation for the determination of Cd²⁺ was about ±4% at the 2 × 10^-5 M level.     

Microcell for anodic stripping voltammetry of trace metals

A microcell for batch injection stripping voltammetry of trace metals with the use of a rotating disk working electrode has been developed and tested for samples of 0.2–0.3 mL. The detection limits for Pb²⁺, Cd²⁺ and Zn²⁺ are 0.03 ppb and 0.3 for a deposition time of 5.0 and 0.5 min, respectively.     

Potentiometric stripping analysis and anodic stripping voltammetry with carbon fiber electrodes

High-modulus carbon fibers are used as working electrodes in differential-pulse stripping voltammetry and potentiometric stripping analysis. Different types of electrodes (particularly single-fiber and brush electrodes) are compared with regard to reproducibility, sensitivity, and practical aspects. Zinc, cadmium, and lead are determined in the 100 μg 1^?1 to 1 mg l^?1 range and optimum experimental parameters are described. The cut single-fiber electrode has the best general characteristics.