engleski

Influence of aqueous phase composition, ionic strength and pH on hydrophobicity of chlorophenols

n-Octanol/water partition coefficient Kow is one of the most important properties of chemicals that could be used for the prediction of their distribution and fate in the environment.The dependence of Kow coefficient of chlorophenols on the aqueous phase composition, ionic strength and pH values was investigated for 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol. Kow was determined in the n-octanol/deionised water, n-octanol/0.01 mol dm-3 CaCl2 and n-octanol/0.05 mol dm-3 CaCl2 aqueous solution systems as a function of aqueous phase pH values (pH 1-10). CaCl2 solutions were used to achieve a better correlation of Kow values with sorption coefficients of chlorophenols in natural sorbents determined with the same aqueous phase composition [1, 2]. Equilibrium chlorophenol concentrations were measured by gas chromatography of acetylated compounds accumulated from aqueous phase by octadecyl (C18) solid-phase extraction columns. The equilibrium concentrations in organic phase were calculated as difference between the initial and equilibrium concentration in aqueous phase. The Kow coefficients of all three chlorophenols decreased as the equilibrium pH values of the aqueous phase increased, which was in accordance with the increase of dissociation of chlorophenols at pH values above their pKa. The effect of CaCl2 concentrations on distribution of chlorophenols between aqueous and organic phase was determined for all compounds at different pH values. [1] Fröbe, Z., Fingler, S., Drevenkar, V. & Juračić, M.: Sci. Total Environ., 155 (1994) 199-213. [2] OECD Guidelines for testing of chemicals, (1996). Adsorption/desorption using a batch equilibrium method. Guideline No. 106.

2;4;6-trichlorophenol; 2;3;4;6-tetrachlorophenol; pentachlorophenol; Kow; hydrophobicity Kow; hidrofobnost

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