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.
Tolls
Johannes
J
Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands. johannes.tolls@henkel.com
Bodo
Karina
K
De Felip
Elena
E
Dujardin
Roland
R
Kim
Yong Hwa
YH
Moeller-Jensen
Lars
L
Mullee
Darren
D
Nakajima
Ayako
A
Paschke
Albrecht
A
Pawliczek
Jürgen-Bernd
JB
Schneider
Jürgen
J
Tadeo
José-Luis
JL
Tognucci
Alessandra C
AC
Webb
Jim
J
Zwijzen
A Corneel
AC
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