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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
March 2020
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:
April 2004
Deviations:
no
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:
3.6
Temp.:
25 °C
pH:
> 5 - < 6

The retention times which were recorded for the reference items are presented in the following table.

Table 9.1 a         Retention Times (RT) Reference Items

Compound

RT 1 [min.]

RT 2 [min.]

RT 3 [min.]

RT 4 [min.]

RT 5 [min.]

RT 6 [min.]

Thiourea

1.377

1.373

1.373

1.373

1.373

1.373

2-Butanone

1.683

1.683

1.683

1.680

1.683

1.683

Acetophenone

2.110

2.110

2.110

2.110

2.110

2.110

Benzene

3.110

3.107

3.110

3.107

3.110

3.110

Naphthalene

5.170

5.170

5.170

5.170

5.173

5.173

Diphenyl ether

6.820

6.820

6.820

6.823

6.823

6.823

Phenanthrene

9.733

9.730

9.733

9.737

9.740

9.740

Fluoranthene

13.463

13.457

13.463

13.470

13.473

13.477

 

For each reference item, the calculated capacity factors are presented in the following table:

Compound

Retention Time mean [min.]

Retention Time Standard Deviation [min.]

Retention TimeRelative Standard Deviation [%]

k

Thiourea

1.374

0.001

0.099

0

2-Butanone

1.683

0.001

0.081

0.2248

Acetophenone

2.110

0.000

0.000

0.5358

Benzene

3.109

0.002

0.055

1.2628

Naphthalene

5.171

0.002

0.033

2.7638

Diphenyl ether

6.822

0.002

0.027

3.9652

Phenan-threne

9.736

0.004

0.041

6.0861

Fluoranthene

13.467

0.007

0.055

8.8023

The values for log k and log Pow of the reference items are presented in the following table:

Compound

log k

log POW

2-Butanone

-0.6481

0.30

Acetophenone

-0.2710

1.70

Benzene

0.1013

2.10

Naphthalene

0.4415

3.60

Diphenyl ether

0.5983

4.20

Phenanthrene

0.7843

4.50

Fluoranthene

0.9446

5.10

 

From the results above a graph could be derived showing log (k) versus log Pow following the equation y = 0.3302*x – 0.7355 (R² = 0.9831)

Correlation results in Dead time being 1.374 ±0.001 minutes, with RSD (relative standard deviation) 0.1%. The RSD of the retention times of the reference items lay all below 0.1 %.

Equation of the regression: log k = 0.3302 * log POW – 0.7355 with a coefficient of determination r² = 0.9831

Measurements of the retention times for the test item 1,3-Diiodopropane were performed in triplicate with results as follows:

Measurement

RT [min.]

Measurement 1

5.323

Measurement 2

5.323

Measurement 3

5.323

Mean

5.323

Standard deviation [%]

0.000

 

Calculated Values for Capacity Factor k, log Capacity Factor and log Pow test item were derived form these data and the calibration curve:

Measurement

k

log k

log POW

Measurement 1

2.8746

0.4586

3.6

Measurement 2

2.8746

0.4586

3.6

Measurement 3

2.8746

0.4586

3.6

Mean

 

 

3.6

Relative Standard deviation [%]

 

 

0.0

 

Where the log Pow was calculated from the capacity factor k as follows: log Pow = (log k + 0.7355) / 0.3302

Result: The chromatogram of the test item 1,3-Diiodopropane gave one peak with a retention time of 5.323 min ±0.000 (mean). Using the correlation log k / log Pow, the log Pow of the test item 1,3-Diiodopropane is calculated with 3.616 ±0.000 (mean ±standard deviation) at the temperature of 25.0 ±0.5 °C.

Validity: The validity criteria and results are presented in the following table:

Peak

Parameter

Criterion

Found

Assessment

1

Range (Max – Min. log Pow)

< 0.1

0.000

valid

 

Value within Range of Ref. Items

1.683 - 13.467

5.323

valid

Conclusions:
The log Pow of 1,3-Diiodopropane is determined as 3.6 at the temperature of 25.0 ± 0.5 °C in this OECD 117 study under GLP.
Executive summary:

The study to determine the log Pow of 1,3-Diiodopropane was performed using a HPLC with a C18 column. Seven reference items with different retention times and thiourea for the determination of the dead time were used to produce a calibration curve, since retention time on hydrophobic columns and Pow are correlated. The reference items were chosen based on the results of a non-GLP pre-test.

One vial was filled with the reference item mix and one vial with the test item solution. The vials were analysed using the HPLC method. First one injection from the solvent blank methanol/water 75/25 (% v/v) was made. Then three injections were measured from the reference item mix, three injections from the test item and again three injections from the reference item mix.

For each reference item, the capacity factor k was calculated from the retention time of thiourea and the retention time of the respective reference item. A calibration function (log k versus log Pow, linear fit) was determined using the literature values for Pow of the reference items and the retention times in the six determinations.

The chromatogram of the test item 1,3-Diiodopropane gave one peak with a retention time of 5.323 min ±0.000 (mean). The log Pow of the test item is calculated with 3.616 ±0.000. Therefore, the log Pow of 1,3-Diiodopropane is stated as 3.6 at the temperature of 25.0 ± 0.5 °C in this study.

Variations in the retention times of reference items and test item are very small. Therefore, a stable configuration of the HPLC-column can be assumed. Also, the correlation log k/log Pow is good and the coefficient of determination r² was calculated with 0.9831. This value was considered as sufficiently high to use the calibration function for the determination of the log Pow of the test item 1,3-Diiodopropane.

No observations were made which might cause doubts concerning the validity of the study outcome.

Description of key information

A study to determine the log Pow of 1,3-Diiodopropane was performed using a HPLC with a C18 column. Seven reference items, chosen based on the results of a non-GLP pre-test, with different retention times and thiourea for the determination of the dead time were used to produce a calibration curve, since retention time on hydrophobic columns and Pow are correlated.

One vial was filled with the reference item mix and one vial with the test item solution. The vials were analysed using the HPLC method. First one injection from the solvent blank methanol/water 75/25 (% v/v) was made. Then three injections were measured from the reference item mix, three injections from the test item and again three injections from the reference item mix.

For each reference item, the capacity factor k was calculated from the retention time of thiourea and the retention time of the respective reference item and a calibration function (log k versus log Pow, linear fit) was determined using the literature values for Pow of the reference items and the retention times in the six determinations.

The chromatogram of the test item 1,3-Diiodopropane gave one peak with a retention time of 5.323 min ±0.000 (mean). The log Pow of the test item was calculated with 3.616 ±0.000. Therefore, the log Pow of 1,3-Diiodopropane is stated as 3.6 at the temperature of 25.0 ± 0.5 °C in this study.

Key value for chemical safety assessment

Log Kow (Log Pow):
3.6
at the temperature of:
25 °C

Additional information