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Partition coefficient

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Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient - Shake Flask Method)
Version / remarks:
September 19, 1984
GLP compliance:
yes
Type of method:
flask method
Analytical method:
high-performance liquid chromatography
Type:
Pow
Partition coefficient:
727.66
Temp.:
21 °C
Remarks on result:
other: pH not given
Type:
log Pow
Partition coefficient:
2.86
Temp.:
21 °C
Remarks on result:
other: pH not given

Contrary to what might be expected in a salt-like compound, the test substance has a true partition coefficient, i.e. it is not dependent on concentration.

Measured and individual values:

 Test

no.

 Concentration

octanol

[mg/mL]

 concentration

water

[mg/mL]

Partition coefficient

individual 

Partition coefficient

group mean 

 1a  1.037095 1.384E-03   749.35     765.67
 1b  1.048636  1.341E-03   781.98
 2a  0.551166  0.828E-03  665.66     716.01
 2b  0.529558  0.691E-03  766.36 
 3a  0.261072  0.359E-03   727.22     701.31
 3b  0.264757  0.392E-03   675.40
Executive summary:

The partition coefficient log Pow of sodium p-chloro-m-cresolate was determined by shake flask method accord EU Method A.8 to be 2.86 at 21 °C.

Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient)
GLP compliance:
yes (incl. certificate)
Remarks:
Ministerium für Arbeit, Integration und Soziales des Landes Nordrhein-Westfalen, Düsseldorf, Germany
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Specific details on test material used for the study:
The test was performed with 4-chloro-m-cresolate, the nonionic form of sodium p-chloro-m-cresolate.
99.9 % 4-chloro-3-methylphenol
Type:
log Pow
Partition coefficient:
2.73
Temp.:
25 °C
pH:
7.2
Remarks on result:
other: 4-chloro-3-methylphenol

The partition coefficient (Pow) of 4-chloro-3-methylphenol, the nonionic form of sodium p-chloro-m-cresolate, was determined according to the HPLC method at 40 °C. In order to comply with the guideline OECD 117 and considering environmental relevance, buffered water at pH 7 was chosen. The reference Pow-values in the OECD-guideline presumably refer to 25 °C. Even though the column temperature was 40 °C, this temperature is without influence on the result of the determination. The calibration was done referring to Pow-values of reference substances determined at 25 °C.

For the determination of the partition coefficient (Pow) six calibration standards with log Pow from 1.3 - 3.2 are established in Regulation EC 440/2008.

The chromatogram of the test item showed 1 signal eluting at 6.2 minutes.

For the partition coefficient of the test item determined by HPLC follows: log Pow = 2.73 at 25 °C (all validity criteria have been met).

Details on Results:

Mean value of 3 single values of the calibration substances:

 Calibration items

 Retention time [tr]

= min

 Capacity

factor k’

 Log k’  Log Pow
 Thiourea (dead time (t0))  1.335   -   -   -
 4-Methoxyphenol  2.443  0.830  - 0.081  1.3
 Phenol  2.742  1.054  0.023  1.5

 p-Cresol

 3.491

 1.614

 0.023

 1.9

 4-Chlorophenol

 4.546

 2.404

 0.381

 2.4

 1-Naphthol

 6.753

 4.057

 0.381

 2.7

 4-Phenylphenol

 8.666

 4.057

 0.793

 3.2

Capacity factor: k’ = (tR - t0)/t0

tR = retention time of substances;

t0 = dead time

Effective correlation: log k’ = a + b log Pow,

Linear regression gives:

a = - 0.64067

b = 0.44018

r = 0.9943

where, a and b = regression factor and r = correlation factor

Determined values of the test item (single values):

 Test item

 Retention

time [tr]

(min)

Test 1

 

Retention

time [tr]

(min)

Test 2

 
 

Retention

time [tr]

(min)

Test 3

 

Standard

deviation

of the

retention

time [tr]

(min) 

Relative

standard

deviation

of the

retention

time [tr]

(%) 

 4-chloro-3-methylphenol  6.199  6.200  6.203  0.0021  0.03

Mean value of 3 single values of the test item:

  Test item   

Retention

time [tr]

(min)

Capacity factor k’  Log k’  Log Pow 
   4-chloro-3-methylphenol  6.201  3.644  3.644 2.73
Conclusions:
For the partition coefficient of the test item 4-chloro-3-methylphenol, the nonionic form of sodium p-chloro-m-cresolate, determined by HPLC follows:
log Pow: 2.73 at 25 °C (all validity criteria have been met)
Executive summary:

The partition coefficient (Pow) of 4-chloro-3-methylphenol, the nonionic form of sodium p-chloro-m-cresolate, was determined according to the HPLC method at 40 °C. In order to comply with the guideline OECD 117 and considering environmental relevance, buffered water at pH 7 was chosen. The reference Pow-values in the OECD-guideline presumably refer to 25 °C. Even though the column temperature was 40 °C, this temperature is without influence on the result of the determination. The calibration was done referring to Pow- values of reference substances determined at 25 °C.

For the determination of the partition coefficient (Pow) six calibration standards with log Pow from 1.3 - 3.2 are established in Regulation EC 440/2008. The chromatogram of the test item 4-chloro-3-methylphenol showed 1 signal eluting at 6.2 minutes.

For the partition coefficient of the test item 4-chloro-3-methylphenol, determined by HPLC follows:

log Pow: 2.73 at 25 °C (all validity criteria have been met).

Description of key information

log Pow = 2.86 at 21 °C (EU Method A.8, shake flask)

logPow = 2.73 at pH 7.2 and 25 °C (nonionic form) (OECD 117, HPLC method)

logD = 2.7 at pH 4

logD = 2.7 at pH 7

logD = 2.6 at pH 9

Key value for chemical safety assessment

Log Kow (Log Pow):
2.73
at the temperature of:
25 °C

Additional information

The partition coefficient log Pow of sodium p-chloro-m-cresolate was determined by shake flask method according to EU Method A.8 to be 2.86 at 21 °C, no information on pH value was given in this study.

Measurements on logPow of ionisable substances should be made in their nonionic form using an appropriate buffer with a pH below the pK for a free acid or above pK for a free base. The nonionic form of sodium p-chloro-m-cresolate is 4-chloro-3-methylphenol (the conjugate acid) and therefore in a further study a test according to OECD Guideline 117, HPLC method, was performed with 4-chloro-3-methylphenol. The pKa value of 4-chloro-3-methylphenol is pKa(acid) = 9.4. Therefore the undissociated form (nonionic form) exists at a pH value < 9.4 and the test was carried out in buffered water at pH 7. A log Pow of 2.73 at pH 7.2 and 25 °C was determined for the nonionic form.

The relevant logD values for the environmentally relevant pH values were calculated by using the pKa value and log Pow = 2.73 at 25 °C.