Spectrophotometric determination of copper(II) with 3-thianaphthenoyltrifluoroacetone

Summary Two visible spectrophotometric methods are described for the determination of Copper(II) with 3-thianaphthenoyltrifluoroacetone at a pH of 4.0. The effect due to pH, time, solvents, reagent concentration and diverse ions are reported. Beer's law is obeyed in both cases and the molar extinction coefficients at 410 and 430 nm are 9.3·10² and 2.9·10² respectively.

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Zusammenfassung Zwei spektrophotometrische Verfahren zur Bestimmung von Kupfer(II) mit 3-Thianaphthenoyltrifluoraceton bei pH 4,0 wurden beschrieben. Der Einfluß von pH, Zeit, Lösungsmitteln, Reagenskonzentration und von diversen Fremdionen wurde ermittelt. Das Beersche Gesetz ist in beiden Fällen erfüllt. Der molare Extinktionskoeffizient beträgt bei 410 bzw. 430 nm 9,3·10² bzw. 2,9·10².

     

Gravimetric determination of copper(II) with p-aminobenzoic acid

A method has been developed for the gravimetric determination of 20-100 mg of copper(II) with p-aminobenzoic acid. Ag, Hg(II), Pb, Al, Fe(II), Bi, Sb(III) and Sn(II) interfere, but Zn, Co(II), Ni and Cd do not. The precipitate can be weighed after drying at 80-100 degrees , or can be ignited to copper(II) oxide at temperatures above 400 degrees , and weighed in this form.     

Non-aqueous redox determination of ascorbic acid with copper (II)

Hydrated copper (II) perchlorate (in acetonitrile) has been used for the direct visual and potentiometric determination of ascorbic acid in acetic acid-acetonitrile media. Diphenylamine and diphenylbenzidine are suitable indicators. A bright platinum wire is used as indicator electrode and a modified calomel or an antimony electrode as reference electrode for the potentiometric titration. Ascorbic acid is oxidized to dehydroascorbic acid. The proposed method is simple, accurate and reliable. The reverse titration also works well.     

Kinetic study of copper(II) complexation with 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone and kinetic-spectrophotometric determination of copper(II)

The kinetics of complexation reaction of Cu(II) with 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone (ECCAT) has been examined spectrophotometrically. The ligand was synthesized for the first time. The complexation reaction was carried out in a DMF-water medium at 35°C. The complex has maximum absorbance at 393 nm. Kinetic and activation parameters of the complexation reaction were calculated by the Arrhenius and Eyring equations using the data obtained from investigating the effect of temperature on reaction rates under the specified conditions. We also proposed reaction rate equations. Based on the studied complexation reaction, a simple kinetic method for the spectrophotometric determination of copper(II) has been developed. The calibration graphs are linear in the concentration range 0.2–1.9 μg/mL. The species that caused interference were investigated. The text was submitted by the authors in English.     

Voltammetric copper(II) determination with a montmorillonite-modified carbon paste electrode

The clay mineral montmorillonite has been tested as modifier for the carbon paste electrode with a novel electrode modification technique. The differential pulse voltammetric determination of copper(II) by means of this modified carbon paste electrode has been studied. A detection limit of 4x10(-8) mol/l has been achieved after 10 min preconcentration under open circuit conditions with subsequent anodic stripping voltammetry. The calibration curve for Cu(II) is linear in the range of 4x10(-8)-8x10(-7) mol/l. Pb interferes in a 10-fold molar and Cd and Hg in a 100-fold molar excess. The interference by humic ligands is significant.     

Voltammetric copper(II) determination with a montmorillonite-modified carbon paste electrode

The clay mineral montmorillonite has been tested as modifier for the carbon paste electrode with a novel electrode modification technique. The differential pulse voltammetric determination of copper(II) by means of this modified carbon paste electrode has been studied. A detection limit of 4×10^-8 mol/l has been achieved after 10 min preconcentration under open circuit conditions with subsequent anodic stripping voltammetry. The calibration curve for Cu(II) is linear in the range of 4×10^-8–8×10^-7 mol/l. Pb interferes in a 10-fold molar and Cd and Hg in a 100-fold molar excess. The interference by humic ligands is significant.     

Spectrophotometric determination of copper(II) using oximidobenzotetronic acid

Summary Oximidobenzotetronic acid (OBTA) is proposed as a sensitive spectrophotometric reagent for the estimation of 0.5–3.0 ppm of copper(II) at 427 nm in 50% dioxan at p_H 5.3–7.5. For the estimation of 2 ppm Cu(II), 1.3 ppm Ni(II), 1.3 ppm Co(II), 3.2 ppm Fe(II), 10.3 ppm Fe(III), 9.7 ppm Ce(IV), 300 ppm acetate, 160 ppm oxalate, 95 ppm tartrate, 50 ppm citrate, as well as Zn(II), Cd(II), Hg(II)) Pb(II), Mn(II), As(III) as well as (V), Th(IV), Be(II), Ce(III), La(III), V(V) and Mo(VI), even when present in large quantities, do not interfere. The interference due to 25 ppm Bi(III), 20 ppm Sb(III), 20 ppm Sn(II), 25 ppm Sn(IV) and 30 ppm W(VI) can be removed by the addition of 95 ppm tartrate ions.

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Zusammenfassung Oximidobenzotetronsäure wurde als empfindliches Reagens zur spektrophotometrischen Bestimmung von 0,5 bis 3,0 ppm Kupfer(II) bei 427 nm in 50%iger Dioxanlösung bei p_H 5,3 bis 7,5 vorgeschlagen. Die Anwesenheit von 1,3 ppm Ni(II), 1,3 ppm Co(II), 3,2 ppm Fe(II), 10,3 ppm Fe(III), 9,7 ppm Ce(IV), 300 ppm Acetat, 160 ppm Oxalat, 95 ppm Tartrat, 50 ppm Citrat sowie die Anwesenheit auch großer Mengen Zn(II), Cd(II), Hg(II), Pb(II), Mn(II), As(III) bzw. (V), Th(IV), Be(II), Ce(III), La(III), V(V) und Mo(VI) stören die Bestimmung von 2 ppm Cu(II) nicht. Der störende Einfluß von 25 ppm Bi(III), 20 ppm Sb(III), 20 ppm Sn(II), 25 ppm Sn(IV) und 30 ppm W(VI) kann durch Zusatz von 95 ppm Tartrat beseitigt werden.

     

Titrimetric determination of mercaptans with chloramine-T

Propyl mercaptan, allyl mercaptan, 2-mercaptoethanol, cysteamine hydrochloride, thio-p-cresol, 2-aminobenzenethiol, 2-mercaptopropionic acid and thioglycollic acid react with chloramine-T in 2:1 molar ratio in the presence of iodide, forming the corresponding disulphides. Mercaptans having a free beta-carbonyl group do not react quantitatively. The oxidation of the mercaptans is a function of time, and the corresponding sulphonic acids are formed on allowing them to stand with excess of chloramine-T. The oxidation to sulphonic acid is, however, instantaneous in the presence of iodine cyanide which acts as a catalyst and preoxidizer. This method is simple, accurate and rapid, and as little as 0.5 mg of the mercaptan can be determined with +/- 0.25% error.     

The micro determination of copper(II) with a solid-state copper-selective electrode

The standard addition and standard subtraction methods are discussed briefly. Both methods are applied to the determination of copper(II) in very small sample volumes. A microcell (25 μl) and a copper-selective micro-electrode are described for this purpose; a nanoliter burette was constructed for the addition of very small increments. The results are compared with those obtained in a 10-ml cell.     

The titrimetric determination of copper(I), copper(II) and copper metal in admixture

Summary Copper(I) can be determined in the presence of copper(II) by oxidation with an excess of potassium iodate, the copper(II) being masked with oxalate. The unconsumed iodate is determined iodimetrically and the total copper is then determined on the same solution by demasking with acid and iodide, followed by iodimetric titration. The method can be extended to include elemental copper which can be separated from copper(I) and copper(II) oxides by dissolving the oxides in an ammonium chloride-ascorbic acid solution. The separated copper metal can then be determined by the iodate procedure. The methods are accurate and reproducible and have been applied to the determination of commercial copper(I) chloride, copper powder and partially oxidized copper powder. The relative standard deviation is about 0.35% in the range of 5.8–100 mg of Cu.

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Trimetrische Bestimmung von Kupfer(I), Kupfer(II) und metallischem Kupfer in Gemischen

Zusammenfassung Cu(I) kann in Gegenwart von Cu(II) durch Oxidation mit überschüssigem Kaliumiodat unter Maskierung des Cu(II) mit Oxalat bestimmt werden. Das unverbrauchte Iodat wird iodometrisch erfaßt und anschließend Gesamtkupfer in derselben Lösung iodometrisch nach Demaskierung mit Säure und Iodid bestimmt. Das Verfahren kann noch auf metallisches Kupfer erweitert werden, das von Cu(I)- und Cu(II)-oxiden abgetrennt wird, indem man letztere in Ammoniumchlorid-Ascorbinsäurelösung löst. Das elementare Kupfer wird dann mit Iodat bestimmt. Die Methoden sind genau und reproduzierbar und sind zur Analyse von handelsüblichem Kupfer(I)-chlorid, Kupferpulver und teilweise oxidiertem Kupferpulver angewendet worden. Die relative Standardabweichung liegt im Bereich von 5,8–100 mg Cu bei 0,35%.

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This paper is respectfully dedicated to Professor Dr. Herbert Weisz on the occasion of his 60th birthday.

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The authors are grateful to Emeritus Professor Ronald Belcher for his interest in this work.     

The determination of anionic detergents with the bis (ethylenediamine)copper(II) ion

A method is described for the determination of anionic detergents. The detergent anions are extracted into chloroform as an ion-association compound with the bis(ethylenediamine)copper(II) cation. Determinations are completed by colorimetry or atomic absorption spectrometry. With a 150-ml water sample, the limit or detection is 0.03 μg ml^-1 (as LAS) for colorimetry or 0.06 μg ml^-1 for a.a.s. The method requires only one phase separation step and is highly selective. It is directly applicable to brine and sea-water samples.     

Periodatometric determination of organotrithiocarbonates and mercaptans (via trithiocarbonate formation)

A method has been described for the direct visual and potentiometric determination of organotrithiocarbonates in bicarbonate medium in the presence of potassium iodide, using potassium periodate as an oxidimetric reagent. The method was extended to the determination of mercaptans after their quantitative transformation to the corresponding organotrithiocarbonates through reaction with carbon disulfide in the presence of alkali. The resulting trithiocarbonates are titrated with periodate in the manner described herein. The excess of carbon disulfide does not interfere in these determinations. Organotrithiocarbonates are smoothly, rapidly, and quantitatively oxidized to the corresponding bis(alkyl/aryl mercapto thiocarbonyl) disulfides with the oxidant under the specified conditions.     

Simultaneous determination of copper(II) and cobalt(II) by ion chromatography coupled with chemiluminescent detection.

In the absence of any special luminescent reagents, a weakly chemiluminescent emission was observed during the decomposition of hydrogen peroxide, catalyzed by transition-metal ions, such as Cu(II) and Co(II), in basic aqueous solution. The chemiluminescent intensity was significantly enhanced by the addition of ethyldimethylcetylammonium bromide and uranine. The signal-to-noise ratio (S/N) was proportional to the concentrations of Cu(II) and Co(II). Based on these phenomena, a flow-injection chemiluminescent method for the simultaneous separation and determination of Cu(II) and Co(II) was developed. The detection limits of the present chemiluminescent method for Cu(II) and Co(II) were 7.5 and 0.01 ng/ml, respectively. After ion chromatographic separation of Cu(II) and Co(II) by an IonPac CS5A column with oxalic acid and lithium hydroxide monohydrate as the eluent, the present chemiluminescent system was used as a post-column detector for these two transition metal ions in natural water samples.     

Specific determination of trace copper(II) by cathodic electroluminescence

Copper (II) stimulates cathodic electroluminescence at the oxide-covered aluminum electrode in the presence of hydrogen peroxide and 2,2′-bipyridine in 0.1 M sodium acetate. The detection limit is 5 × 10^?9 M; no other metal ions interfered. The mechanism of the reactions is discussed.