Amidinourea phosphate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July - August 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Chemical name: Amidinourea phosphate
- CAS No.: 75701-36-9
- Molecular formula: C2H6N4O.H3PO4
- Molecular weight: 200.1 g/mol

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Samples of the different aqueous extracts were collected at time 0, 2 hours, and after 5 days.

Buffers:

CITRATE BUFFER (0.05 M): pH 4
23 g of potassium dihydrogen citrate were dissolved in 1 L of water. An aliquot of 0.50 L was mixed with 0.09 L of 0.1 M NaOH and filled up with water to 1 L to give a pH of 4. The pH was checked with a calibrated pH meter to be 4.07 at 20 °C.

PHOSPHATE BUFFER (0.05 M): pH 7
13.6 g of potassium dihydrogen phosphate were dissolved in 1 L of water. An aliquot of 0.50 L was mixed with 0.296 L of 0.1 M NaOH and filled up with water to 1 L to give a pH of 7. The pH was checked with a calibrated pH meter to be 7.10 at 20 °C.

BORATE BUFFER (0.05 M): pH 9
19 g of sodium tetraborate decahydrate were dissolved in 1 L of water. An aliquot of 0.85 L was mixed with 0.15 L of 0.1 M HCl (prepared from 10 M HCl, Chemsolute, 32 %) to give a pH of 9. The pH was checked with a calibrated pH meter to be 9.10 at 20 °C.

Estimation method (if used):

none

Details on test conditions:

A stock solution of the test item was prepared by accurately weighing 200 mg of guanylurea phosphate into a 10 mL volumetric flask using an analytical balance and dissolving it in water (resulting concentration of analyte: 20.0 mg/mL). A fortification solution with 2 g/L (mg/mL) was prepared by dilution of the stock solution with Millipore water. Calibration solutions of Guanylurea Phosphate were prepared by volumetric dilution of the stock solution using milli-pore water as a solvent

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

>= 150 - <= 20 000 mg/L

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

>= 150 - <= 20 000 mg/L

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

>= 150 - <= 20 000 mg/L

Number of replicates:

Hydrolysis testing at each pH level was performed with three replicate test solutions and one blank for each buffer solution.

Positive controls:

yes

Negative controls:

yes

Statistical methods:

none

Preliminary study:

A preliminary hydrolysis experiment (Tier 1) was conducted as the hydrolytic behavior of the test substance was unknown so far. All three-buffer solution were spiked with test substance to achieve an end concentration of 1.0 g/L.

Test performance:

The preliminary test was performed at 50 ± 0.5°C for 5 days applying aqueous buffer solutions at pH 4, 7 and 9. Samples of the different aqueous extracts were collected at time 0, 2 hours, and after 5 days. Collected aliquots were further diluted and analysed by HPLC/UV allowing the detection of ≤ 10 % of the time 0 levels of the test substance in the buffer solutions.

Transformation products:

no

Details on hydrolysis and appearance of transformation product(s):

no significant hydrolysis observed, therefore no transformation products analyzed

% Recovery:

> 100

St. dev.:

2.1

pH:

4

Temp.:

50 °C

Duration:

5 d

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

> 100

St. dev.:

1.6

pH:

7

Temp.:

50 °C

Duration:

5 d

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

98.4

St. dev.:

98.4

pH:

9

Temp.:

50 °C

Duration:

5 d

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Details on results:

The average recoveries obtained in Tier 1 testing were always in the range of 98-102 %. Test analyte was hydrolyzed less than the 10 %. This indicated a sufficient hydrolytic stability of Guanylurea Phosphate in different buffer solutions after 5 days of incubation at 50 °C. No significant hydrolysis (≤ 10 %) was observed in the preliminary test at 50 °C for all tested pH values (4, 7, 9) of guanylurea phosphate. This indicates a half-life period of Guanylurea Phosphate at 25 °C of more than 1 year (t0.5 25°C > 1 year). Thus, the test substance Guanylurea Phosphate was considered to be hydrolytically stable and a further testing (Tier 2 experiments) (according to OECD guideline 111) was not required.

Results with reference substance:

No reference substance tested

Validity criteria fulfilled:

yes

Conclusions:

No significant hydrolysis (≤ 10 %) was observed in the preliminary test at 50 °C for all tested pH values (4, 7, 9) of guanylurea phosphate. This indicates a half-life period of Guanylurea Phosphate at 25 °C of more than 1 year (t0.5 25°C > 1 year). Thus, the test substance Guanylurea Phosphate was considered to be hydrolytically stable and a further testing (Tier 2 experiments) (according to OECD guideline 111) was not required.

Executive summary:

The objective of the study was to assess the abiotic hydrolytic transformation of the test item in aquatic systems at three different pHs (4.0, 7.0, and 9.0). Experiments were performed to determine the rate of hydrolysis as a function of pH and temperature considering requirements of OECD Guideline 111. The preliminary test was performed at 50 ± 0.5°C for 5 days applying aqueous buffer solutions at pH 4, 7 and 9. Samples of the different aqueous extracts were collected at time-0, 2 hours, and after 5 days. Collected aliquots were further diluted and analysed by HPLC/UV allowing the detection of ≤ 10 % of the time-0 levels of the test substance in the buffer solutions.

The test lab successfully performed the hydrolysis testing for Guanylurea Phosphate in aquatic systems at three different pHs (4, 7, and 9) demonstrating the hydrolytic stability of the test substance after 5 days incubation at 50 °C (Tier 1). Thus, no further hydrolysis experiments (Tier 2) were deemed to be necessary. The half-life period for the analytes at 25 °C was assumed to be more than 1 year (t0.5 25°C > 1 year).

Description of key information

No significant hydrolysis (≤ 10 %) was observed in the preliminary test at 50 °C for all tested pH values (4, 7, 9) of guanylurea phosphate. This indicates a half-life period of Guanylurea Phosphate at 25 °C of more than 1 year (t 1/2 at 25°C). Thus, the test substance Guanylurea Phosphate was considered to be hydrolytically stable and a further testing (Tier 2 experiments) (according to OECD guideline 111) was not required.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

Source: GLP-study