Disodium β-glycerophosphate

Partition coefficient

Administrative data

Endpoint:

partition coefficient

Type of information:

other: Expert Statement supported by experimental data

Adequacy of study:

key study

Study period:

20 - 24 November 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Well documented expert statement supported by experimental data

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 - 09 August 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

1995

Deviations:

yes

Remarks:

see principles of method if other than guideline

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

Regulation (EC) No 440/2008

Deviations:

yes

Remarks:

see principles of method if other than guideline

Principles of method if other than guideline:

Due to very high water solubility of the test item, estimated in a preliminary test, a modified TG OECD 105 design was conducted. Instead of equilibrating a large amount of test item with water by stirring over several days and subsequently separating the test item from the saturated solution, water was added in a stepwise procedure to a defined amount of test item until complete dissolution occurred.

GLP compliance:

yes (incl. QA statement)

Remarks:

determination of total phosphorus was performed by a third laboratory under the QA system ISO/IEC 17025 and is therefore excluded from the statement of GLP compliance

Type of method:

flask method

Key result

Water solubility:

>= 379 g/L

Conc. based on:

test mat. (dissolved fraction)

Temp.:

22 °C

pH:

10

Details on results:

Preliminary test
Approximately 1 g of the test item were completely dissolved in 2.4 mL of ultra-pure water indicating a water solubility of about >=420 g/L.

Main test
The results are given in the table in the next section. The water solubility was determined as the mean of the triplicate test assays analysed. As this method does not ensure complete saturation of the solution, it is given as minimum value in mass per volume of solution. The test is satisfactory, if the concentrations of the three vessels do not differ by more than 15%.

Analytical determinations:                                                               

Test vessel	pH	Analysed concentration A^(1) (g/L)	Analysed concentration B^(1) (g/L)	Analysed concentration A^(2) (g/L)	Analysed concentration B^(2) (g/L)	Mean (g/L)
No. 1	10	53.0	52.7	384	381	382
No. 2	10	51.6	52.3	373	378	376
No. 3	10	52.1	52.2	377	378	377
					Overall Mean	379

(1) Determined total phosphorous concentrations

(2) Determined test item concentrations

The concentrations of the three vessels differed by 2% (validity criterion given by OECD is met).

Further remarks:

Based on the test item amount used (ca. 1 g) and the volume of ultra-pure water applied (2.3 ml) to achieve complete dissolution, a theoretical solubility of ca. =435 g/l results, which is significantly higher than the water solubility determined in this test. It has to be considered in this case that the final volume of the test item solution is most likely higher than just the 2.3 ml of the ultra-pure water added, due to the very high test item concentrations.

Conclusions:

The water solubility of Disodium beta-glycerophosphate (CAS no. 819-83-0) was determined according to a modified TG OECD 105 design.
The water solubility of the test item at 22°C was >= 379 g/L. The pH of the aqueous solutions was 10.

Executive summary:

The water solubility of the test item Disodium beta-glycerophosphate (CAS no. 819-83-0) was determined according to a modified TG OECD 105 design. To this end, increasing volumes of water were added in a stepwise procedure, to approximately 1 g of the test item at 22 ± 2 °C until complete dissolution, which occurred after addition of 2.3 mL of ultra-pure water. The concentration of test item was subsequently determined by total phosphorous analysis. The determined water solubility of Disodium beta-glycerophosphate is >=379 g/L at pH 10 and at 22 °C.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)

Version / remarks:

1995

Deviations:

not applicable

Remarks:

not applicable for expert statement

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient - Shake Flask Method)

Version / remarks:

Regulation (EC) No 440/2008

Deviations:

not applicable

Remarks:

not applicable for expert statement

Principles of method if other than guideline:

The objective of this expert statement was to assess the log POW of Disodium beta-glycerophosphate by consideration of both, theoretical as well as experimental data.

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Type of method:

flask method

Partition coefficient type:

octanol-water

Test material

Test material information

Constituent 1

Reference substance name:

Disodium β-glycerophosphate

EC Number:

212-464-3

EC Name:

Disodium β-glycerophosphate

Cas Number:

819-83-0

Molecular formula:

C3H7O6P.2Na

IUPAC Name:

disodium β-glycerophosphate

impurity 1

Reference substance name:

Disodium α-glycerophosphate

EC Number:

216-304-3

EC Name:

Disodium α-glycerophosphate

Cas Number:

1555-56-2

Molecular formula:

C3H9O6P.2Na

IUPAC Name:

disodium 2,3-dihydroxypropyl phosphate

impurity 2

Reference substance name:

Water

EC Number:

231-791-2

EC Name:

Water

Cas Number:

7732-18-5

Molecular formula:

H2O

IUPAC Name:

Oxidane

Test material form:

solid: particulate/powder

Details on test material:

Batch No.: 11769400
Storage: 15-25°C

Study design

Analytical method:

photometric method

Results and discussion

Partition coefficient

Key result

Type:

log Pow

Partition coefficient:

< 0

Temp.:

21 °C

pH:

>= 5 - <= 9

Details on results:

Theoretical considerations
The log POW of Disodium beta-glycerophosphate is estimated to be -6.96 (EPI Suite™ v4.11; KOWWIN v1.68). This predicted value is out of the range of the EPI Suite training set (log POW values >= -5). Nevertheless, it may be used as indication that the log Pow of the test item is very low. Thus, this test is most likely out of the scope of the OECD 107 test (log Pow of -2 to 4) as well as the OECD 117 test (log Pow of 0 to 6) and the OECD 123 test (log Pow >=4) tests.
According to TG OECD 107, this test should be conducted with the non-ionized form and in the environmentally relevant pH range of pH 5 to 9. In the case of Disodium beta-glycerophosphate, the once and twice negatively charged forms predominate in the environmentally relevant range.

Flask method
It was not possible to determine the log POW value of Disodium beta-glycerophosphate, as the determination of the test item concentrations was based on the analysis of total phosphorous, which could only be conducted reliably in the aqueous phase.
However, the experimental data obtained in this study demonstrates that the test item concentrations in the 1-octanol phase must have been negligibly low, as the mass balance calculation based on the aqueous phase alone resulted in recoveries of 104% to 110% (i.e. a log Pow of 0 would correspond to recoveries of about 50%).

Any other information on results incl. tables

Ratio n-octanol:water (v:v)	Phase	Solvent volume (L)		Determined phosphorous concentration (mg/L)	Determined test item concentration (mg/L)*	Mass balance: Nominal amount of test item(mg)	Mass balance: Total found** (mg)	Mass balance: Recovery rate(%)***
Ratio 1:4_A	1-Octanol Aqueous buffer	0.020 0.080		n.d. 260	n.a. 1881	144	151	104
Ratio 1:4_B	1-Octanol Aqueous buffer	0.020 0.080		n.d. 270	n.a. 1954	144	156	108
Ratio 1:9_A	1-Octanol Aqueous buffer	0.010 0.090		n.d 270	n.a. 1954	162	176	108
Ratio 1:9_B	1-Octanol Aqueous buffer	0.010 0.090		n.d. 275	n.a. 1990	162	179	110
Ratio 1:19_A	1-Octanol Aqueous buffer	0.005 0.095		n.d. 273	n.a. 1972	172	187	109
Ratio 1:19_B	1-Octanol Aqueous buffer	0.005 0.095		n.d. 268	n.a. 1936	172	184	107

* Calculated using a total phosphorous content of 13.82% in the test item

** Determined test item concentration in aqueous phase x solvent volume of aqueous phase

*** Percentage of total determined in the aqueous phase / nominal introduced into the system

n.d.: Not determined

n.a.: Not applicable

Further remarks:

Additional evidence for the polarity of the test item and thus a corresponding low log POW value is the water solubility of the test item, which is >=379 g/L (as determined in the water solubility study, see cross-ref). Furthermore, the predicted log POW by EPI Suite™ v4.11 is -6.96 (KOWWIN v1.68).

Applicant's summary and conclusion

Conclusions:

The experimental and theoretical data provided in this expert statement illustrate that Disodium beta-glycerophosphate (CAS no. 819-83-0) most likely has a log POW significantly below zero in the environmentally relevant pH range of 5 to 9.

Executive summary:

It was the aim of this study to assess the log POW of the test item Disodium beta-glycerophosphate (CAS no. 819 -83 -0). To this end, theoretical and experimental data were assembled as presented in this study.

For the experimental part, a test to determine the log POW according to TG OECD 107 was performed: aqueous buffer solution at pH 6.7, 1-octanol and the test item were equilibrated in test vessels by shaking, applying three different volume ratios of the two solvents. The analysis of the test item concentrations was based on total phosphorous, which could only be conducted reliably in the aqueous phase. As the solubility of the test item in 1-octanol is very likely to be poor, no measurements were performed in the 1-octanol phase and consequently no log POW values could be calculated.

The experimental data obtained demonstrate that the test item concentrations in the 1-octanol phase must have been negligibly low, as the mass balance calculation based on the aqueous phase alone resulted in recoveries of 104% to 110% (i.e. a log Pow of 0 would correspond to recoveries of about 50%).

Additional evidence for the polarity of the test item and thus a corresponding low log POW value is the water solubility of the test item, which is >=379 g/L (as determined in the water solubility study). Furthermore, the predicted log POW by EPI Suite™ v4.11 is -6.96 (KOWWIN v1.68).

The experimental and theoretical data provided in this expert statement illustrate that Disodium beta-glycerophosphate most likely has a log POW significantly below zero in the environmentally relevant pH range of 5 to 9.