N-glycylglycine

Partition coefficient

Administrative data

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 June - 24 June 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)

Version / remarks:

2004

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient - HPLC Method)

Version / remarks:

Commission Regulation (EC) No 440/2008

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC method

Partition coefficient type:

octanol-water

Test material

Test material information

Constituent 1

Reference substance name:

N-glycylglycine

EC Number:

209-127-8

EC Name:

N-glycylglycine

Cas Number:

556-50-3

Molecular formula:

C4H8N2O3

IUPAC Name:

N-glycylglycine

Test material form:

solid: crystalline

Details on test material:

Batch Number: S119 0711
Storage conditions: room temperature

Specific details on test material used for the study:

Batch no.: S119 0711
Test item storage: at room temperature, protected from light

Study design

Analytical method:

high-performance liquid chromatography

Results and discussion

Partition coefficient

Key result

Type:

log Pow

Partition coefficient:

<= -0.92

Temp.:

25 °C

pH:

6

Remarks on result:

other:

Remarks:

calculated as the mean of two determinations

Details on results:

Theoretical value of the log Pow
The log Pow value of the non-ionised test item species is -2.92 (experimental database match; Hansch C. et al., (1995); EPI Suite v4.11).

HPLC method

The dead time was determined to be 1.364 min.

Two determinations of the log Pow value of the test item were conducted by injecting a mixed solution of all reference items as well as the single test item solution twice using a phosphate buffered system at pH 6.0.
The retention time of the single test item peak in both injections was shorter than the one for Thiourea, which was used as dead time marker. Therefore, an extrapolation based on the regression data obtained by the injection of reference items was not possible. Instead, the log Pow of Glycyl-glycine was estimated and is given as less than or equal to the one of Thiourea corresponding to <=-0.92.

Consequently, the log Pow value of Glycyl-glycine at pH 6.0 and 25 °C is <=-0.92.

Any other information on results incl. tables

Exemplary regression data for the determination of the log Pow value of Glycyl-glycine, plot log Pow vs. log k:

Coefficient of regression (r2)	0.975
Intercept (A)	1.830
Slope (B)	2.15
log Pow	not applicable
95% confidence interval of log Pow	not applicable

Applicant's summary and conclusion

Conclusions:

The HPLC method was applied for the determination of the log Pow of Glycyl-glycine.

The retention time of the single test item peak in both injections was shorter than the one for Thiourea, which was used as dead time marker. Therefore, an extrapolation based on the regression data obtained by the injection of reference items was not possible. Instead, the log Pow of Glycyl-glycine was estimated and is given as less than or equal to the one of Thiourea corresponding to <=-0.92.

Consequently, the log Pow value of Glycyl-glycine at pH 6.0 and 25 °C is <=-0.92.

Executive summary:

The partition coefficient between octanol and water (Pow) of Glycyl-glycine (CAS no. 556-50-3) was determined according to the OECD guideline 117. This determination is based upon a regression analysis of the log Pow values of reference items against their respective retention times as determined by HPLC analysis.

The following reference items were used: Caffeine, 4-Acetylpyridine, Acetanilide, Acetophenone, Methyl benzoate, Benzophenone and Benzyl benzoate. The dead time of the HPLC system was determined with Thiourea.

This set of reference items yielded a calibration with log Pow values ranging from -0.07 to 4.0 and retention times ranging from 1.497 to 11.647 minutes. The dead time of the HPLC system was 1.364 minutes.

The retention time of the single test item peak in both injections was shorter than the one for Thiourea, which was used as dead time marker. Therefore, an extrapolation based on the regression data obtained by the injection of reference items was not possible. Instead, the log Pow of Glycyl-glycine was estimated and is given as less than or equal to the one of Thiourea corresponding to =-0.92.

Consequently, the log Pow value of Glycyl-glycine at pH 6.0 and 25 °C is =-0.92.

From a theoretical point of view, log Pow only applies to the partitioning of the non-charged species between 1-octanol and the aqueous phase. Based on model calculations for the species distribution of Glycyl-glycine as function of the pH, the test item species are always ionised in the pH range of 0 to14 and predominantely zwitterionic at pH 6.0 so that the value determined in this study very likely corresponds to a log Dow.

The validity criterion as given in the guideline cannot be applied in this case, as the test item peak eluted before the dead time marker Thiourea. However, both injections were consistent, as the determined retention time was identical.