Titration Of Copper Research Articles

Use of sodium dodecyl sulphate to clarify the end-point of anodic-stripping complexometric titrations

It has been found that addition of sodium dodecyl sulphate will completely suppress the dissociation of the copper-EDTA complex at the electrode surface in the anodic-stripping complexometric titration of copper and make the end-point of the titration very clear. The addition of SDS also makes it possible to titrate traces of nitrilotriacetic acid, which forms a copper complex that is less stable than the EDTA complex. The effect of SDS is presumed to be due to electrostatic repulsion between the negative charges of adsorbed SDS and the metal complex at the electrode surface.

Differential electrolytic potentiometry with ion-selective electrodes for end-point detection in compleximetric titrations of mercury(II), copper(II), nickel(II) and bismuth(III)

Electrodes prepared by activating hydrophobized spectrographic graphite rods with various mercury(II) chalcogenides, alone or mixed with silver(I) chalcogenides or mercury itself, were used successfully in differential electrolytic potentiometry (d.e.p.) to locate end-point in compleximetric titrations of mercury(II) solutions with EDTA. Several materials gave useful d.e.p. peaks at the expected end-point, showing that these electrodes can replace the commoner mercury and amalgamated gold electrodes. To demonstrate the usefulness of the sensors in EDTA titrations of metal ions other than mercury(II), titrations of copper(II) were performed. The electrode response takes place via reaction of the ion with sulphide of selenide in the electroactive layer. Electrodes activated by copper(II), bismuth(III), nickel(II) chalcogenides were also studied; those sensors that produced good ion-selective electrodes were also useful in d.e.p. titrations.

Semi-automatic catalytic titration of aminopolycarboxylic acids and metal ions with the 4,4′-dihydroxybenzophenone thiosemicarbazone - hydrogen peroxide - copper(II) system

A semi-automatic spectrophotometric method is described for the catalytic titration of EDTA and ethylene glycol bis(β-aminoethyl ether)-NN′-tetraacetic acid (EGTA), based on their inhibitory effect on the copper(II)-catalysed oxidation of 4,4′-dihydroxybenzophenone thiosemicarbazone by hydrogen peroxide. Amounts of EDTA and EGTA in the 370–1100 and 380–1 140 µg ranges, respectively, can be determined with a relative standard deviation of about 0.5%(n= 11). Methods are also described for the indirect catalytic titrations of copper(II), nickel(II) and manganese(II), in the range 10–120 µg, with a relative standard deviation of about 0.6%(n= 11).

Interaction of copper(II) ions with the daunomycin-calf thymus deoxyribonucleic acid complex.

The interaction of Cu(II) with the native and heat-denatured DNA complexes of daunomycin (1) and N-(trifluoroacetyl)daunomycin (3) has been examined by using absorption and circular dichroism spectroscopies. At low rt, where rt is the input molar ratio of drug to DNA phosphate, Cu(II) interacts with the native and heat-denatured calf thymus DNA complex of daunomycin to form a ternary complex involving the aglycon portion of the antibiotic, Cu(II), and DNA. A Job plot of the titration involving Cu(II) and heat-denatured DNA shows that the Cu(II)-drug stoichiometry in the ternary complex is less than or equal to 1. Although the N-(trifluoroacetyl)daunomycin-native DNA complex does not form a ternary complex, the denatured DNA complex with the antibiotic does. Copper(II) titrations of the daunomycin-native DNA complex, at high rt, where both strongly and weakly bound antibiotic molecules are very likely present in solution result in the formation of both the ternary species as well as a binary complex involving only the metal ion and the antibiotic. The spectroscopic results indicate that in the ternary complex, the Cu(II) ion is bound to the unintercalated aglycon portion of the antibiotic and very likely also to the heterocyclic bases of DNA.

Development and analytical applications of a new liquid-membrane 3,5-dinitrosalicylate-selective electrode

A 3,5-dinitrosalicylate (DNS)-selective electrode with a liquid membrane of either tetraphenyIphosphonium-DNSH dissolved in p-nitrocumene or dimethyldioctadecylammonium-DNSH dissolved in 1-decanol is described. The liquid membrane electrode exhibits rapid and near-Nemstian response to DNSH- activity from 10 -2 to 10 -5 M. The response is unaffected by pH in the range 2.5–6.5. The electrode has been successfully applied in the direct potentiometric titration of iron(III) and copper(II) with EDTA and in the indirect titrimetric determination of aluminium(III) and nickel(II). It is also useful in titrations of bulky quaternary cations such as cetyltrimethylammonium, cetylpyridinium and didodecyldimethylamnionium ions with DNSHNa.

Surface-tension titration of metal ions by using metal salts of fatty acids as surface-active indicators

The use of calcium and zinc salts of stearic, palmitic and myristic acids as surface-active indicators has been investigated in various buffer solutions. The back titration of nickel(II), cobalt(II) and their mixture with calcium chloride and the direct titration of copper(II) with EDTA has been successfully performed by using calcium palmitate and calcium stearate, respectively, as surface-active indicator. The end point, which is indicated by a remarkable change in surface tension, agrees well with the equivalence point.

Amperometric titration of copper with ammonium dithiocarbamate and its determination in the presence of cadmium and mercury

Ammonium dithiocarbamate has been standardized with EDTA solution and its use for the estimation of milligram quantities of copper has been reported. Copper is titrated at +0.2 V vs SCE in ammonium tartrate-potassium nitrateammonia buffer using the rotating platinum micro-electrode. Copper has also been estimated in binary solutions with cadmium and mercury. The accuracy of the procedure is comparable to that obtained with other classical methods.

Copper(II) titration of fulvic acid ligand sites with theoretical, potentiometric, and spectrophotometric analysis

Copper(II) titration of fulvic acid ligand sites with theoretical, potentiometric, and spectrophotometric analysis

EDTA titrations of copper, lead and nickel with 1-(2-pyridylazo)-2-naphthol or its copper chelate indicator in the presence of a surface active agent

1-(2-Pyridylazo)-2-naphthol (PAN) reacts with Cu2+ over the wide pH range. Al:1 (metal-toligand ratio) chelate with an absorption maximum at 555nm is formed in acidic solution, and a 1:2 chelate (abs. max. 558nm) in alkaline solution. Both chelates are insoluble in water, but can be solubilized in the presence of non-ionic surfactants. EDTA titrations of metals with PAN and Cu-PAN indicators are therefore facilitated with them. The optimum conditions for such titrations, and especially the rate of color change in the course of the titration of Cu2+ with PAN, were studied. The rate (obtained with the assumption of a pseudo-first order law) is increased by the surfactants such as Triton X-100 and Brij 35 all over the course of titration, and the addition of dioxane is effective only near the end point. In the presence of Triton X-100 surfactant, Pb2+ can be titrated with Cu-PAN indicator at pH 3.44.3twice as quickly as in the absence, Ni2+ can be titrated at pH3.5 with a very sharp end point in the presence of Brij 35 at 80°C, where Triton X-100 was ineffective because of its low cloud point.

Vanadium(III) as an analytical reagent: The titrimetric determination of iron, copper, thallium, molybdenum, uranium, vanadium, chromium and manganese

Vanadium(III) solutions can be used in direct titrations of iron(III), copper(II), thallium(III), molybdenum(VI), uranium(VI), vanadium(V), chromium(VI) and manganese(VII) in milligram amounts. The titrations are done at 70–80° for iron(III), copper(II), thallium(III), molybdenum(VI) and at room temperature for vanadium(V), chromium(VI) and manganese(VII). Uranium(VI) is titrated at 70–80° in presence of iron(II). The vanadium(III) solution is prepared by reduction of vanadium(V) to vanadium(IV) with sulphur dioxide, followed by addition of phosphoric acid and reduction with iodide, and is reasonably stable.

Potentiometric determination of copper complexation by phytoplankton exudates 1

Potentiometric copper titrations were done on culture media in which eight algal species, Thalassiosira pseudonana (3H), Ankistrodesmus falcatus, Chlamydomonas sp., Pediastrum sp., Staurastrum gracile, Gloeocystis gigas, Tribonema sp., and Cyclotella cryptica were grown to cell concentrations of 105–106 cells · ml−1. The results demonstrate that only G. gigas produces extracellular organic compounds that can measurably reduce the cupric ion activity in 1 × 10−6 M total copper.

Tropolone as an extractive indicator in EDTA titrations of copper in alloys

Tropolone as an extractive indicator in EDTA titrations of copper in alloys

Molar absorption coefficients of porphyrin esters in chloroform determined by copper titration.

Chromatographically pure porphyrin esters free from metalloporphyrins were titrated with Cu2+ to determine the molar amount of porphyrin present. The end point of the titration was defined by a t.l.c. method detecting traces of metal-free porphyrin ester in admxture to its copper complex. From spectrometric measurement at the Soret maximum and the molar amounts found by the titration, epsilonM was calculated for proto-, copro-, penta-, hexa- and hepta-carboxylic and uro-porphyrin permethyl esters. The values for uroporphyrin showed perfect agreement with those of previous workers, whereas those for coproporphyrin were about 5% lower and those for protoporphyrin more than 20% lower. The implications of the findings are discussed. Determinations of epsilonM of some higher esters (ethyl to pentyl) and some partial methyl esters with one carboxyl group free are also presented.

Liquid-membrane type 8-quinolinol-5-sulfonate ion selective electrode and its application to potentiometric titration

A nitrobenzene extract of the ion-pair consisting of 8-quinolinol-5-sulfonate (Hqs−) and the cation of zephiramine (Z+Cl−, benzyldimethyltetradecylammonium chloride) was used as an ion-exchanging liquid membrane for the electrode responding to Hqs− ion. The potential response showed the Nernstian slope with the Hqs− activities varying from 10−2 to 10−4.5 mol l−1. The break points in the potential-pH plot with the constant analytical concentration of H2qs correspond to the values of the negative logarithm of the acid dissociation constant of H2qs. The present electrode was successfully applied to the potentiometric titration of copper(II) with H2qs.

Liquid-membrane type 8-quinolinol-5-sulfonate ion selective electrode and its application to potentiometric titration

A nitrobenzene extract of the ion-pair consisting of 8-quinolinol-5-sulfonate (Hqs −) and the cation of zephiramine (Z +Cl −, benzyldimethyltetradecylammonium chloride) was used as an ion-exchanging liquid membrane for the electrode responding to Hqs − ion. The potential response showed the Nernstian slope with the Hqs − activities varying from 10 −2 to 10 −4.5 mol l −1. The break points in the potential-pH plot with the constant analytical concentration of H 2qs correspond to the values of the negative logarithm of the acid dissociation constant of H 2qs. The present electrode was successfully applied to the potentiometric titration of copper(II) with H 2qs.

The chalcocite copper membrane electrode

The membrane electrode based on a synthetic chalcocite (Cu 2S) single crystal responds primarily to the activity of copper(I) ions in solution. The experimental selectivity coefficient with respect to copper(II) ions is in good agreement with the value calculated on the basis of solubility products of both sulphides. The electrode has been calibrated with metal-ion buffers containing a strongly complexing ligand. TETREN, and can be used as an indicator in titrations of copper with EDTA and TETREN. Comparison of an experimental titration curve with one calculated with the aid of the program HALTAFALL showed good agreement in the case of TETREN, but there were discrepancies for the EDTA titration, which are attributed to the presence and complexation of copper(I) ions. The electrode has also been applied in metal titrations with Cu 2+ as indicator ion, though the potential changes observed were smaller than predicted. All titrations showed errors less than 1%.

Niobium(III) as an analytical reagent. : Part I. The titrimetric determination of iron, copper, thallium,molybdenum, uranium and vanadium

Niobium(III) solutions can be used in direct titrations of copper(II), iron(III), thallium(III), moIybdenum(VI), vanadium(V) and uranium(VI) in milligram amounts. Phenosafranine is generally satisfactory as the indicator, but potentiometric end-points can also be used. Copper and iron can be determined successively when a mixed indicator containing phenosafranine and méthylene blue is used. Thallium(I) and thallium (III) can be determined in mixtures. The niobium (III) solutions are stable for several days under a carbon dioxide atmosphere.

A self-generating third-order electrode: Part I. Titrations of transition metal, sulphide, and chloride ions with a silver-silver sulphide electrode

Ag/Ag 2S electrodes were prepared by electrolytic deposition of silver sulphide on a silver rod. These electrodes responded in a Nernstian fashion to cadmium(II) in the pCd range 2.0–10.6; they gave satisfactory results in titrations of silver(I), copper(II), cadmium(II) and zinc(II) with sodium sulphide solution, in titrations of copper(II) and cadmium(II) with EDTA solution, and in titrations of chloride with silver(I) solution. The electrode appears to behave as a third-order selfgenerating electrode. The Ag/Ag 2S electrode was found to be reliable, stable over long periods, unaffected by light under normal laboratory conditions and convenient in use.

The interference of heteronuclear chromium(III) tartrate complexes in the EDTA titration of cobalt(II), copper(II), zinc(II) and cadmium(II)

When present together in solution, chromium(III) and tartrate can interfere seriously in the titration of Co(II), Cu(II), Zn(II) and Cd(II) with EDTA. Ternary (heteronuclear) tartrate complexes containing Cr(III) and bivalent metal ion in the ratio 1:1 are formed. The conditions for the formation of these complexes have been investigated. Cadmium(II) can be determined without interference by employing potentiometric end-point detection.

Design and construction of a fluorotitrator

An instrument is described that permits fluorometric titrations in a large, open compartment that accommodates titration vessels of a wide variety of shapes and sizes. The influence of ambient light is excluded by applying geometric exclusion in combination with electronic monitoring and compensation. In test titrations of copper and calcium with EDTA and calcein, the instrument performed satisfactorily.