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Physical & Chemical properties

Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
May 22nd, 2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Version / remarks:
2004
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient - HPLC Method)
Version / remarks:
2008
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Type:
log Pow
Partition coefficient:
4.53
Temp.:
20 °C
pH:
7.1
Details on results:
-Preliminary test: the preliminary test at room temperature showed that the octanol solubility of the test item was below 1.6 g/l. With the solubility in octanol of <1.6 g/l (120 mg were in 75 ml of octanol) and the water solubility <4.39 mg/l, the partition coefficient can be estimated to be approx. 2.6. For the determination of the log Pow at this value the HPLC method is recommended and carried out.

-Main test: after measurements of the retention times tr, the log k values of the reference items were plotted as a function of their log Pow values. The partition coefficient of the test item was obtained by interpolation of the calculated capacity factor on the calibration graph of the reference items.
The first measurement and the linear regression of the calibration graph leads to an equation for the log Pow of: log Pow = 3.888 × logk + 3.448, where correlation coefficient r = 0.9884.
The second measurement and the linear regression of the calibration graph leads to an equation for the log Pow of: log Pow = 3.882 × logk + 3.449, where correlation coefficient r = 0.9884.

Preliminary tests for the octanol solubility

Amount of test item [mg] Total volume of octanol [ml]

Stirring time at RT

[min]

Remark
120 5 50 not dissolved
25 45 not dissolved
75 175 not dissolved

Retention time of the dead time marker

  1strun 2ndrun mean value
t0(min) 1.639 1.639 1.639

Retention times of the reference items (1stmeasurement)

reference item tR k log k log Pow[1]
Acetanilide 2.029 0.238 -0.624 1
4-Methyl benzyl alcohol 2.168 0.323 -0.491 1.6
Cinnamyl alcohol 2.198 0.341 -0.467 1.9
Allyl phenyl ether 3.182 0.941 -0.026 2.9
Diphenyl ether 4.133 1.522 0.182 4.2
Fluoranthene 6.938 3.233 0.51 5.1
4,4’ DDT 9.391 4.73 0.675 6.5

[1] Literature values of log Pow from OECD guideline 117 (2004)

Retention times of the reference items (2ndmeasurement)

reference item tR k log k  log Pow[1]
Acetanilide 2.026 0.236 -0.627 1

4-Methyl benzyl

alcohol

2.167 0.322 -0.492 1.6
Cinnamyl alcohol 2.199 0.342 -0.466 1.9
Allyl phenyl ether 3.183 0.942 -0.026 2.9
Diphenyl ether 4.133 1.522 0.182 4.2
Fluoranthene 6.944 3.237 0.51 5.1
4,4’ DDT 9.395 4.732 0.675 6.5

[1] Literature values of log Pow from OECD guideline 117 (2004)

Retention times of the test item

test item tR  k log k log Pow Pow
1stmeasurement 4.757 1.902 0.279 4.534 34213
2ndmeasurement 4.759 1.904 0.28 4.535 34256
mean value 4.534 34235
standard deviation < 0.01 21
Conclusions:
log Pow = 4.53 ± 0.01 at 20 °C and pH 7.1.
Executive summary:

In this study the HPLC method was used. The principle of the HPLC method is based on a reverse phase HPLC, performed on analytical columns packed with a solid phase containing long hydrocarbon chains chemically bound onto silica. The test item injected on such column partitions between the mobile solvent phase and the hydrocarbon stationary phase as it is transported along the column by the mobile phase. The chemicals are retained in proportion to their hydrocarbon-water partition coefficient, with hydrophilic chemicals eluted first and lipophilic chemicals last. As mobile phase, eluents of methanol/water ratios with a minimum water content of 25 % should be used. Alternatively, acetonitrile or 2-propanol can be used instead of methanol. The octanol/water partition coefficient of the test item can be computed by experimentally detemining its capacity factor k and then inputting k into the following equation: log Pow = a+b × logk, where a,b= linear regression coefficients.

The equation above can be obtained by linearly regressing the log of octanol/water partition coefficients of reference substances against the log capacity factors of the reference substances.

The partition coefficient of the test item at 20 °C and pH 7.1 was determined by means of the HPLC method to be: log Pow = 4.53 ± 0.01.

Description of key information

log Pow = 4.53 ± 0.01 at 20 °C and pH 7.1.

Key value for chemical safety assessment

Log Kow (Log Pow):
4.53
at the temperature of:
20 °C

Additional information

HPLC method as described in the OECD guideline 117 (2004).