Disodium 4-nitrophenyl phosphate

Partition coefficient

Administrative data

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 - 23 September 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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:

09 - 10 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, a modified TG OECD 105 design was conducted. Instead of equilibrating a large amount of test item (about five times in excess) 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)

Type of method:

flask method

Key result

Water solubility:

>= 294 g/L

Conc. based on:

test mat. (dissolved fraction)

Temp.:

22 °C

pH:

8

Details on results:

Preliminary test
This preliminary test indicated a water solubility of 200-1000 g/L, as ca. 0.1 mg of the test item were completely dissolved in 0.5 mL of ultra-pure water.

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 with HPLC. As this method does not ensure complete saturation of the solution, it is given as a 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%.

HPLC determinations:

Test vessel	pH	Analysed concentration A (g/L)	Analysed concentration B (g/L)	Mean (g/L)
No. 1	8	295	293	294
No. 2	8	293	294	293
No. 3	8	293	296	294
			Overall Mean	294

The concentrations of the three vessels differed by 0.2% (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 (2.8 ml) to achieve complete dissolution, a theoretical solubility of ca. =360 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 2.8 ml of the ultra-pure water added, due to the very high test item concentrations.

Conclusions:

The water solubility of 4-Nitrophenyl phosphate disodium salt (CAS no. 4264-83-9) was determined according to a modified TG OECD 105 design.
The water solubility of the test item at 22°C was >=264 g/L. The pH of the aqueous samples was 8.

Executive summary:

The water solubility of 4-Nitrophenyl phosphate disodium salt (CAS no. 4264-83-9) 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 2.8 mL of water. The concentration of test item was subsequently determined by HPLC with UV detection. The determined water solubility of 4-Nitrophenyl phosphate disodium salt is >=294 g/L at pH 8 and at 22 °C.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

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:

yes

Remarks:

see "Principles of method if other than guideline"

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:

yes

Remarks:

see "Principles of method if other than guideline"

Principles of method if other than guideline:

The test was not performed with the non-charged species, as given in the guideline, as the amount of non-charged species in the environmentally relevant pH range of 5 to 9 is negligible. Instead, the single and double negatively charged species dominate.
According to the guideline, log POW values between -2 and 4 can be determined. The one determined for 4-Nitrophenyl phosphate disodium salt in this study is slightly out of this range. However, as this was expected based on an estimated value of -4.16 (EPI Suite™ v4.11, KOWWIN v1.68), the focus of this study was to demonstrate that the log POW of the test item at an environmentally relevant pH is indeed very low.

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Partition coefficient type:

octanol-water

Test material

Test material information

Constituent 1

Reference substance name:

Disodium 4-nitrophenyl phosphate

EC Number:

224-246-5

EC Name:

Disodium 4-nitrophenyl phosphate

Cas Number:

4264-83-9

Molecular formula:

C6H4NO6P.2Na

IUPAC Name:

disodium 4-nitrophenyl phosphate

impurity 1

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

Details on test material:

Batch Nr: 11674900
Storage: 2-8°C.

Study design

Analytical method:

high-performance liquid chromatography

Results and discussion

Partition coefficient

Key result

Type:

log Pow

Partition coefficient:

< -2.16

Temp.:

22 °C

pH:

6.7

Remarks on result:

other: The determined log POW values were < -2.16 for all three volume ratios and all replicates. Std. deviation from six determinations: ± 0.001.

Details on results:

Calculation method
The log Pow of the test item was calculated to be -4.16 using EPI Suite™ v4.11, KOWWIN v1.68.
This is out of the scope of the OECD 107 test (log Pow of -2 to 4, see section 3) as well as the OECD 117 test (log Pow of 0 to 6) and the OECD 123 test (log Pow >=4). According to the guideline, this test should be conducted with the non-ionized form. However, in the environmentally relevant pH range of pH 5 to 9, the amount of non-charged species is negligible.
Instead, the singly and double negatively charged species dominate.

Flask method
The determined log POW values were <-2.16 for all three volume ratios and all replicates. For each replicate, the mass balance calculation showed that the experiment was reliably conducted, as the recovery rates ranged from 102% to 103%.
The log Pow of the test item is given as the mean value of all measurements. Detailed results are given in the table in the field 'Any other information on results incl. tables'.

Any other information on results incl. tables

Ratio n-octanol:water (v:v)	Analysed concentration n-octanol (mg/L)	Analysed concentration water (mg/L)		Pow	log Pow	pH
1:4	<21.3	3093	<0.00689		<-2.16	6.7
1:4	<21.3	3068	<0.00695		<-2.16	6.7
1:9	<21.3	3077	<0.00693		<-2.16	6.7
1:9	<21.3	3073	<0.00694		<-2.16	6.7
1:19	<21.3	3067	<0.00695		<-2.16	6.7
1:19	<21.3	3076	<0.00693		<-2.16	6.7
Mean					<-2.16

Further remarks:

The result obtained in this study is in line with the estimated log POW of -4.16 (EPI Suite™ v4.11, KOWWIN v1.68) as well as a determined water solubility of >=294 g/l at pH 8 and 22 °C (see cross-ref to water solubility study).

Applicant's summary and conclusion

Conclusions:

The shake flask method according to TG OECD 107 was applied for the determination of the log Pow of 4-Nitrophenyl phosphate disodium salt (CAS no. 4264-83-9). The determined log Pow value at pH 6.7 is <-2.16 with a standard deviation of ± 0.001.

Executive summary:

The log POW of the test item 4-Nitrophenyl phosphate disodium salt (CAS no. 4264-83-9) was determined according to TG OECD 107.

Aqueous phosphate buffer 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. Subsequently, the test item concentrations were determined in both solvent phases.

The determined log POW values were <-2.16 for all three volume ratios and all replicates. For each replicate, the mass balance calculation showed that the experiment was reliably conducted, as the recovery rates ranged from 102% to 103%.

The determined log POW value of 4-Nitrophenyl phosphate disodium salt at pH 6.7 is <-2.16 with a standard deviation of ± 0.001.

The validity criterion was fulfilled.