Interaction of lead(II) with beta-cyclodextrin in alkaline solutions |
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Authors: | Norkus Eugenijus Grinciene Giedre Vaitkus Rimantas |
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Affiliation: | Institute of Chemistry, A Gostauto 9, LT-2600, Vilnius, Lithuania. norkus@ktl.mii.lt |
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Abstract: | Polarographic and UV-spectrophotometric investigations of Pb(II) complex formation with beta-cyclodextrin have showed that the complexation of Pb(II) ions begins at pH >10. The formation of lead(II) 1:1 complex with the beta-cyclodextrin anion was observed at pH 10-11.5. The logarithm of the stability constant of this complex compound is 15.9+/-0.3 (20 degrees C, ionic strength 1.0), and the molar extinction coefficient value is ca. 5500 (lambda(max)=260 nm). With further increase in solution pH the Pb-beta-cyclodextrin complex decomposes and converts to Pb(OH)(2) or Pb(OH)(3)(-) hydroxy-complexes. This process occurs with a decrease in Pb(II) complexation degree. The latter result could be explained by a decrease in the beta-cyclodextrin anion activity. Neither Pb(OH)(2) nor Pb(OH)(3)(-) encapsulation into beta-CD cavity was observed. |
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Keywords: | β-Cyclodextrin Lead(II) Complex formation |
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