betadex and 2-4-6-trichlorophenol

The solubility of 2,4,6-trichlorophenol (TCP) in hydroxypropyl-beta-cyclodextrin (HPbetaCD), or methyl-beta-cyclodextrin (MebetaCD) at pH 3.0 and 8.8 reported by Hanna et al. [J. Hazard. Mater. B100 (2003) 109] is reevaluated in this paper. The complexations of the individual dissolved forms were examined. As expected, the neutral TCP complexes more strongly with the cyclodextrins than the charged species. However, in spite of its lower complexation constant, the charged form of TCP forms more complex with each CD, and thus is solubilized to a greater extent.

Topics: 2-Hydroxypropyl-beta-cyclodextrin; beta-Cyclodextrins; Chlorophenols; Cyclodextrins; Excipients; Mutagens; Solubility; Water

The solubilities of the neutral and charged forms of 2,4,6-trichlorophenol (TCP) in beta-cyclodextrin (beta-CD) and two of its most used derivatives: methyl-beta-cyclodextrin (MCD) and hydroxypropyl-beta-cyclodextrin (HPCD) solutions were investigated. The three cyclodextrins were found to form 1:1 inclusion complexes. Binding constants estimated from an enhancement solubility method revealed that the stability of the complexes was dependent on the polarity of the compound and on the cyclodextrin used.In general, weaker binding constants were observed for TCP with beta-CD than with HPCD or MCD. The solubilization efficiencies towards TCP can be ranked in the following order: MCD > HPCD > beta-CD. For all cyclodextrins, the stability constant of neutral TCP (logK(ow)=3.85) was larger than that of charged TCP (logK(ow)=1.4).A precipitation occurred in TCP/beta-CD solution (around 10 g/l beta-CD concentration) at pH 3. However, this phenomenon is not observed for TCP/beta-CD solution at pH 8.8.

Topics: 2-Hydroxypropyl-beta-cyclodextrin; beta-Cyclodextrins; Carcinogens; Chemical Precipitation; Chlorophenols; Cyclodextrins; Mutagens; Soil Pollutants; Solubility