Hydrophobicity of complex organic mixtures.

Hydrophobicity is an important property in risk assessment of chemicals. A group parameter that reflects the hydrophobicity of technical mixtures is not yet available. However, many substances are complex organic mixtures, for which it is practically impossible to determine each component separately. An experimental procedure to measure the hydrophobicity of organic mixtures without knowledge of the individual components was developed and tested for a mixture of benzene and twelve chlorobenzenes. This procedure is based on separation of the mixture into fractions of increasing hydrophobicity by reversed-phase HPLC, after which the total molar concentration in each fraction is determined by vapour pressure osmometry. The obtained information on hydrophobicity can be used for assessing bioaccumulation and sediment sorption after emission of the mixture to water has occurred.