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Mass fraction of the organic chemical in the gas phase

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Rosy's picture
Mass fraction of the organic chemical in the gas phase

Dear USEtox team,

I'm studying USEtox.

I tried to demonstrate the equation (8) in the USEtox Documentation.

I arrive a this equation (I attach file)

I can't understand why we introduce the term Kow, app, pH7
I have another question in the equation 10 there is an error.
This is the same condition of equation 39 but in the equation 39 we have a second term at 
denominator of the fraction.
Thanks a lot for your availability



File Demonstration_equation_8.docx14.93 KB
USEtox Team
USEtox Team's picture
Gas phase partitioning

USEtox documentation, equation 8: Apparent Kow is used here as a (measured or calculated) value of the octanol-water partition coefficient at pH=7. Some QSAR equations use this to calculate the extent of partitioning of the chemical from water, which depends on the degree of ionization at ambient-water pH.

USEtox documentation, equation 10: there was indeed a term missing here in the documentation; however, this equation is correctly implemented in the model. We have corrected the USEtox documentation accordingly.