Chlorimuron ethyl

Partition coefficient

Administrative data

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1983

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

A 100 ppm solution of [14C-phenyl-labeled)]-test substance in pH 7 buffer was repeatedly equilibrated with octanol until the Kow value became constant and the octanol and water phase samples were analyzed by thin layer chromatography to determine what fraction of the total 14C measured by liquid scintillation counting was test substance and Kow values were calculated based on these data.

GLP compliance:

not specified

Type of method:

other: Thin layer chromatography

Partition coefficient type:

octanol-water

Test material

Test material information

Constituent 1

Reference substance name:

ethyl 2-({[(4-chloro-6-methoxypyrimidin-2-yl)carbamoyl]amino}sulfonyl)benzoate

EC Number:

618-690-2

Cas Number:

90982-32-4

Molecular formula:

C15H15ClN4O6S

IUPAC Name:

ethyl 2-({[(4-chloro-6-methoxypyrimidin-2-yl)carbamoyl]amino}sulfonyl)benzoate

Test material form:

solid

Remarks:

White

Details on test material:

95 to >99% purity

Specific details on test material used for the study:

[14C-phenyl]-test substance
Radiochemical purity: > 99%

Study design

Analytical method:

other: Thin layer chromatography

Results and discussion

Partition coefficient

Key result

Type:

Pow

Partition coefficient:

1.3

Temp.:

25 °C

pH:

7

Remarks on result:

other: measured

Details on results:

The "apparent" and corrected Kow values for the six consecutive partitioning experiments are listed in Table 1.

"Apparent" Kow values were calculated using the total 14C concentration data for each pair of octanol and water phase samples.

Corrected Kow values were calculated from the TLC analyses to correct for the actual concentration of test substance in each sample.

The relative fractions of test substance and other 14C-compounds was determined from scans of the TLC plates on the Berthold scanner.

The autoradiograms confirmed the 14C-compounds positions identified with the plate scanner. Extraneous 14C-compounds were only detected in the water phase samples and they increased in concentration with each partitioning step. The percentage of 14C-test substance in these samples decreased from 94 to 51% of the total radioactivity. As many as three compounds were detected in the water samples. They were not identified, but none of these compounds had the same Rf value as the principal hydrolysis product, 2-(aminosulfonyl) benzoic acid, ethyl ester. The compounds had lower Rf values than test substance and so were apparently more polar compounds.

After correcting the "apparent" Kow values for % test substance concentration, the Kow values became very reproducible after the first partitioning step. The average Kow of test substance is 1.3 ± 0.2, placing it in the category of compounds having a low bioaccumulation potential (Kow <100).

Any other information on results incl. tables

Table 1: Kow values for consecutive octanol/water partitionings of test substance at pH 7 and 25°C

Partition number	Apparent Kow	Corrected (log Pow)		Average of No. 2-5
		Kow	Std Dev.
1	0.93	0.96	0.1	1.3 (Std.Dev – 0.2)
2	1.28	1.3	0.1
3	1.21	1.2	0.1
4	0.94	1.4	0.3
5	0.61	1.4	0
6	0.18	-	-

Applicant's summary and conclusion

Conclusions:

log Kow of 1.3 at pH 7 and 25°C

Executive summary:

An octanol/water partition coefficient (Kow) value of 1.3 was measured for the soybean herbicide candidate test substance, placing it in the class of compounds having low bioaccumulation potential (Kow <100). For the test, a 100 ppm solution of [14C-phenyl-labeled)]-test substance in pH 7 buffer was repeatedly equilibrated with octanol until the Kow value became constant. Octanol and water phase samples were analyzed by thin layer chromatography to determine what fraction of the total 14C measured by liquid scintillation counting was test substance and Kow values were calculated based on these data.