Method for testing for bioaccumulation

Abstract

For use in estimating or predicting bioaccumulation of a chemical analyte, even a surfactant, log P ow values for the analyte may be determined by calculating the log of the ratio of the concentrations of the analyte in n-octanol and in water, equilibrated using a slow-stir method. In this method, samples of the analyte are prepared and stirred in n-octanol and water (or other largely immiscible solvents) at a rate sufficiently low to avoid emulsions over time at a constant temperature. After stirring, the n-octanol layer and the water layer are sampled and the quantity of analyte in each measured.

1. A method for obtaining a log P value of a chemical for use in chemical bioaccumulation analysis, said method comprising:
 providing a sample of said chemical in two largely immiscible solvents;  
 allowing said sample to equilibrate at constant temperature over time;  
 determining the concentration of the chemical in each of the solvents; and  
 calculating the partition coefficient.  
 
   
   
     2. The method of  claim 1  further comprising stirring said sample to expedite said equilibration at a rate sufficiently slow that emulsions do not occur. 
   
   
     3. The method of  claim 1  wherein said chemical is a surfactant. 
   
   
     4. The method of  claim 1  wherein said solvents are water and n-octanol. 
   
   
     5. The method of  claim 4  wherein said temperature is in the range of about 20° C. to about 22° C. 
   
   
     6. The method of  claim 1  wherein said temperature is below the boiling point of said solvents and said chemical. 
   
   
     7. The method of  claim 1  wherein said time extends over several days or weeks. 
   
   
     8. The method of  claim 4  wherein said calculation is made using the equation: 
         P   ow     =         c     n   ⁢     -     ⁢   octanol         c   water       ⁢           .         
 
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     9. A method for obtaining a log P value of a surfactant for use in surfactant bioaccumulation analysis, said method comprising:
 providing a sample of said surfactant in two largely immiscible solvents,  
 stirring said sample at constant temperature and at a rate sufficiently slow that emulsions do not occur over time while allowing equilibration of said sample;  
 determining the concentration of the surfactant in each solvent, and calculating the partition coefficient of the surfactant.  
 
   
   
     10. The method of  claim 9  wherein said rate of stirring provides a vortex in said sample such that the ratio of the length of the fluid column of said sample to the vortex height ranges from about 1 to about ∞. 
   
   
     11. The method of  claim 9  wherein said rate of stirring provides a vortex in said sample such that the ratio of the length of the fluid column of said sample to the vortex height ranges from about 4 to 5. 
   
   
     12. The method of  claim 9  wherein said partition coefficient is calculated using the following formula: 
       P   =         c     (     lighter   ⁢           ⁢   solvent     )         c     (     heavier   ⁢           ⁢   solvent     )         ⁢           .         
 
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     13. The method of  claim 9  wherein the solvents are water and n-octanol and the following equation is used in calculating said partition coefficient: 
         P   ow     =         c     n   ⁢     -     ⁢   octanol         c   water       ⁢           .         
 
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     14. The method of  claim 13  wherein said temperature is in the range of about 20° C. to about 22° C. 
   
   
     15. The method of  claim 9  wherein said temperature is below the boiling point of said solvents and said surfactants.