Speciation 98: Abstracts

The use of the supramolecules frequently needs the knowledge of their coordination ability towards different metal ions. Many times however a comprehensive coordination chemistry studies with supramolecules is limited because their available amount is small. Therefore for coordination chemistry studies - specially for determination of stability constants - methods using small amount of supramolecules are necessary.

For determination of composition and stability constants of europium complexes with some supramolecules the competitive spectrophotometric method was chosen. To find an appropriate competitive agents the complex formation between europium(III)ion and different dyes were studied by spectrophotometry. Firstly the spectra's of solutions of dyes in presence and in absence of europium(III) ion were analysed in pH=1 - 10 range to determine whether is there a complex formation or not. From the investigated dyes, forming complexes with europium(III) ion the xylenol orange(XO), the methylthymol blue(MTB) and the arzenazo III(AA) dyes were chosen for detailed studies.

The complex formation between europium(III)ion and XO, MTB and AA was investigated in different buffer system in pH=6-8 range. Phosphate, veronal and hepes buffer systems were tested and the hepes proved to be appropriate. The composition and stability constants of europium(III) complexes with XO, MTB and AA were determined in pH=6-8 range. For determination of composition the Job method was used.

Using the competitive spectrophotometric method - with XO, MBT and AA as competitive agents - the stability constants of europium(III)complexes with two supramolecules were determined.