Slow-stirring method for determining the n-octanol/water partition coefficient (Pow) for highly hydrophobic chemicals: performance evaluation in a ring test.
The n-octanol/water partition coefficient (Pow) is one of the most important parameters employed for estimating a chemical's environmental fate and toxicity. The currently adopted test guidelines for its determination do not allow for reliable determination of log Pow greater than 5. The slow-stirring experiment, in contrast, has been demonstrated to provide reliable log Pow data up to log Pow of 8.3. To validate this method and to obtain its approval as an official Organization for Economic Cooperation and Development (Paris, France) test guideline, a ring test was performed to evaluate the accuracy and precision of the slow-stirring experiment for determination of log Pow, particularly for highly hydrophobic compounds. Up to 15 volunteer laboratories tested 1,2,3,4-tetrachlorobenzene, hexachlorobenzene. 2,2',3,3',5,5',6,6'-octachlorobiphenyl, and decachlorobiphenyl (4.5 < log Pow < 8.2). The ring-test results for the respective chemicals were 4.62, 5.50, 7.39, and 8.18. The results deviated by less than 0.1 log Pow units from the reference log Pow. In addition, the relative standard deviations of log Pow were less than 2%. Using the protocol of the ring test, log Pow of p,p'-DDT was determined to be 6.24 +/- 0.05 (mean +/- standard deviation). In combination, these results indicate that the slow-stirring method is precise and accurate and, thus, allows for reliable determination of log Pow of highly hydrophobic chemicals.
Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands. johannes.tolls@henkel.com
Johannes
J
Tolls
Karina
K
Bodo
Elena
E
De Felip
Roland
R
Dujardin
Yong Hwa
YH
Kim
Lars
L
Moeller-Jensen
Darren
D
Mullee
Ayako
A
Nakajima
Albrecht
A
Paschke
Jürgen-Bernd
JB
Pawliczek
Jürgen
J
Schneider
José-Luis
JL
Tadeo
Alessandra C
AC
Tognucci
Jim
J
Webb
A Corneel
AC
Zwijzen
D005069:Evaluation Studies as Topic; D057927:Hydrophobic and Hydrophilic Interactions; D007753:Laboratories / Q000592:standards* / Q000706:statistics & numerical data; D000442:Octanols / Q000737:chemistry*; D012015:Reference Standards; D015203:Reproducibility of Results; D012995:Solubility; D014867:Water / Q000737:chemistry*
D000442:Octanols; D014867:Water