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Complexing interactions of arsenazo III

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dc.contributor.advisor Rohwer HE, Prof en
dc.contributor.author Hosten EC en
dc.date.accessioned 2016-09-22T13:19:02Z
dc.date.available 2016-09-22T13:19:02Z
dc.date.submitted 1996 en
dc.identifier.uri http://hdl.handle.net/20.500.11892/157498
dc.description.abstract Arsenazo III is an excellent chromogenic reagent for the photometric analysis of many metal ions. In the literature discrepancies exist regarding the stoichiometrics of the complexes of arsenazo HI with several metal ions. Furthermore factors affecting complex formation, such as pH and the interactions of anions, have not been adequately investigated and serve as an incentive for this study on the reactions of arsenazo HI with the lanthanides(III) and uranium(VI) under various conditions.<br><br> Spectrophotometric pH titrations show that the 1:1 arsenazo III - lanthanide complexes have four distinct protonation states in the pH range 1-11. All the lanthanides exhibit the same trends with small variations in the calculated formation and molar absorptivity constants. Similarly the 1:1 arsenazo in - uranium(VT) complex also exhibits four different protonation states.<br><br> Mole ratio titrations and mole fraction plots show that under moderately acidic conditions the lanthanides form only a single 1:1 complex, while under weakly acidic and alkaline conditions both a 1:1 and a 1:2 (Az:Ln) complex form. Uranium(VI) is different in that, under all conditions tested, only a 1:1 complex forms. Furthermore uranium(VI) is able to react with arsenazo III under strongly acidic conditions (> 6 M HC10<sub>4</sub>).<br><br> It is shown that under moderately acidic conditions, anions have a strong influence on the complexation of arsenazo HI with the lanthanides and uranium(VI). In the presence of excess anions the lanthanides form 1:1:1 and 2:1:1 Az:Ln:X complexes (X = anion) together with the normal 1:1 complex. Uranium(VI) in the presence of excess anions forms only the 1:1 and 1:1:1 Az:U0<sub>2</sub>:X complexes. The formation of the MX species with both the lanthanides and uranium(VI) occurs at high anion concentrations.<br><br> Extraction studies of arsenazo III and its complexes with aliquat in chloroform, show that arsenazo III is also capable of forming a variety of different complexes in an organic phase.<br><br> This study has shown that the reactions of arsenazo in with the lanthanides(III) and uranium(VI) are strongly dependent on the pH value and the anion concentration, which makes it imperative that these factors be taken into account when using arsenazo III as an analytical reagent. en
dc.language English en
dc.title Complexing interactions of arsenazo III en
dc.type Masters degree en
dc.description.degree MSc en


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