Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2021-05-06 - 2021-05-21

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

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on test conditions:

All buffer solutions were filled in glass bottles and purged with N2 for five minutes.
Afterwards the buffer solutions were sterilized at 120 °C for 20 minutes. Before the beginning of the tests, the solutions were tempered, and the temperature was checked.
Approx. 900 mg of the test item were dissolved in 250 mL buffer solution resulting in a test item concentration of 3.6 g/L (0.01 mol/L).
Aliquots of the test solution were directly filled into brown glass sample vials to obtain individual samples for each test point. Preparation was carried out under nitrogen as flushing gas to avoid oxygen.
All glassware was purged with N2 before and after filling in the test item and the buffer solutions. The test solutions were overlain with N2.
The vials were closed and incubated at 50 °C in a heat regulator with electronic temperature control to the exclusion of light to avoid any photolytic effects. The temperature was checked during the experiment using a digital precision thermometer. No deviations above ± 0.5 °C from the target value were obtained.
At the beginning and after 5 days at 50 °C the test solutions were analysed by NMR-spectroscopy (13C and 31P nuclei). The buffer solutions were also measured as buffer blanks before sample treatment.
The pH of the blank buffer solution was checked at the beginning of the test as well as after dissolving the test item.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

3.6 g/L

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

3.6 g/L

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

3.6 g/L

Test performance:

According to OECD TG 111 the concentration of the test item should not exceed 0.01 M or half of the saturation concentration of the water solubility.
The water solubility of the test item was determined in the high g/L range (Currenta Study no.: 2020/0089/02).
Consequently, the test item was applied as aqueous buffer solution with a concentration of approx. 3.6 g/L which fulfills the requirements of OECD 111 (equals to approx. 0.01 mol/L). Clear solutions were obtained.
In compliance with OECD 111 no test with organic solvent additives > 1% (v/v) was performed.

Transformation products:

no

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

No indication for a hydrolysis can be found and no half-life times and hydrolysis rates were determined. No further tests at other temperatures or pH values are required.

Key result

pH:

4

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

9

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

7

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Details on results:

The test item solutions were measured directly after preparation and after five days. In addition, the pH buffer blank solutions were measured. From all solutions 13C- and 31P-NMR spectra were recorded.
A quantitative evaluation of the measurements was not possible. The qualitative evaluation of the NMR spectra shows no significant differences between T = 0d and T = 5d for all three pH values. Thus, no indication for a hydrolysis can be found and no half-life times and hydrolysis rates were determined. No further tests at other temperatures or pH values are required.
The test item is considered to be hydrolytically stable.
Remark:
Differences in the intensities can be caused by slightly differences in the concentrations of the NMR solutions. Changes in the chemical shifts (ppm) can be caused by differences in the temperatures due to the direct measurements (solutions obtained at 50 °C).

Validity criteria fulfilled:

yes

Conclusions:

No abiotic degradation of the test item was observed.
Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate is found to be stable at 50 °C at all three pH-values. No indications for a degradation were found. Therefore, it can be assumed that the test item is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.
The test item is considered to be hydrolytically stable.

Executive summary:

For each pH value separate hydrolysis test solutions were prepared in the corresponding buffer systems. Test item concentrations of approx. 3.6 g/L were obtained. Aliquots of the stock solutions were taken without further treatment to prepare individual vials for every test point.  

No abiotic degradation of the test item was observed.

Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate is found to be stable at 50 °C at all three pH-values. No indications for a degradation were found. Therefore, it can be assumed that the test item is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.

The test item is considered to be hydrolytically stable.

Description of key information

No indication for a hydrolysis after 5 days at 50 °C can be found and no half-life times and hydrolysis rates were determined. No further tests at other temperatures or pH values are required.

Additional information

Phosphonic acids are known to be stable towards hydrolysis even at extreme pH values and temperatures. Tetrasodium hydrogen 2-phosphonatobutane-1,2,4-tricarboxylate is a highly effective scale and corrosion inhibitor. Reflecting the stability in water main fields of application are the treatment of cooling and process water as well as the area of cleaning formulations.