Interaction of lead(II) with beta-cyclodextrin in alkaline solutions.
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.
Norkus
Eugenijus
E
Institute of Chemistry, A Gostauto 9, LT-2600, Vilnius, Lithuania. norkus@ktl.mii.lt
Grinciene
Giedre
G
Vaitkus
Rimantas
R
D002413:Cations, Divalent; D003505:Cyclodextrins / Q000737:chemistry*; D004058:Diffusion; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007854:Lead / Q000737:chemistry*; D009994:Osmolar Concentration; D011048:Polarography; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D047392:beta-Cyclodextrins
D002413:Cations, Divalent; D003505:Cyclodextrins; D012996:Solutions; D047392:beta-Cyclodextrins; D007854:Lead; C031215:betadex