Cupferron complexes

Determination of uranium with cupferron Discussion. Cupferron does not react with uranium(VI), but uranium(IV) is quantitatively precipitated. These facts are utilised in the separation of iron, vanadium, titanium, and zirconium from uranium(VI). After precipitation of these elements in acid solution with cupferron, the uranium in the filtrate is reduced to uranium(IV) by means of a Jones reductor and then precipitated with cupferron (thus separating it from aluminium, chromium, manganese, zinc, and phosphate). Ignition of the uranium(IV) cupferron complex affords U308. 

Analytical techniques such as adsorptive stripping voltammetry rely on complex formation to improve detection limits of metals such as V(IV) and V(V) [51]. An example is in the use of cupferron and KBr03 as additives to acidic aqueous solutions, which result in the adsorption of the V(V)-cupferron complex to the electrode surface that catalyzes the reduction of the Br03 ion in solution. This technique has good selectivity over Cu, Pb, Cd, Fe, and Ti, but the response is dependent on pH. 

A selection of the known dioxouranium(VI) complexes with this type of ligand is given in Table 84. These compounds are precipitated from aqueous solution, usually after the addition of alkali. The coordination geometry of the anion in the ammonium salt of the cupferron complex, NH4[U02 (0N)N(Ph)0 3], is close to hexagonal bipyramidal.332... 

Protactinium can be separated from natural ore concentrates by cycles consisting of adsorption on Mn02 precipitates followed by solvent extraction of the cupferron complex with pentyl acetate.94... 

Separation of iron ( Fe) with cupferron complex, and nickel ( Ni) with dimethylglyoxime complex (DMG)2Ni... 

There is also evidence for complexes with hexamethylphos-phoramide, 4-aminophenazone, and N-methyl and N-dimethyl acetamide. But an earlier report of a cupferron complex was not confirmed (39). 

Alivisatos and collaborators [257] demonstrated that transition metal oxide nanocrystals (7-Fc203, Mn304, CU2O) could be prepared using a nonhydrolytic process based on the thermal decomposition of metal Cupferron complexes M Cup (M = metal ion. Cup = CeHsNjNOjO ) in a hot solvent with surfactant. Their results suggest that a good level of control can be achieved when this approach is used to process metal oxide nanoparticles. 

Standards and Blank Samples. When extraction systems are used, it must be taken into account that the analyte is not always transferred completely into the organic phase. The extraction efficiency depends on the conditions such as pH of the aqueous phase and metal-ligand ratio. In addition to the organic solvent used, the ligand may also have an influence on the sensitivity of the analyte in FAAS. Thus, the sensitivity of the analyte may differ in the same solvent when different ligands are used, since the metal—ligand bonds in metal complexes formed possess different thermal properties. For example, the Mn sensitivity in MIBK is better with the cupferron complex than with the diethyldithiocarbamato or 8-hydroxyquinolato complexes. 

In aqueous food samples, plutonium can be separated by precipitation of bismuth phosphate and extraction of the cupferronate complex in chloroform. Finally, plutonium is precipitated by using an iron(III) carrier and measured by means of an a-ray spectrometer. 

Wang, J. and Setiadji, R. (1992). Selective determination of trace uranium by stripping voltammetry following adsorptive accumulation of the uranium cupferron complex. Anal. Chim. Acta 264, 205-211. 

Kefala G, Economou A, Voulgaropoulos A (2006) Adsorptive stripping voltammetric determination of trace uranium with a bismuth-fihn electrode based on the U(VI) -> U(V) reduction step of the uranium-cupferron complex. Electroanalysis 18 223... 

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