Dibutyl hydrogen phosphate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-09-25 till 2012-10-22

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

Buffers:

Buffer pH 4, Fa. Fluka, Citric acid/NaOH/NaCl, Art-Nr.: 33643
Buffer pH 7, Fa. Fluka, KH2PO4/Na2HPO4, Art-Nr.: 33646
Buffer pH 9, Fa. Fluka, Na2B4O7/HCl, Art-Nr.: 33648

Details on test conditions:

The hydrolysis behaviour of dibutyl hydrogen phosphate was investigated at 50 °C at pH 4, pH 7 and pH 9 over a period of five days according to OECD TG 111. The stability was monitored by HPLC analysis using MS-detection.
Dibutyl hydrogen phosphate was dissolved in buffer solutions of pH 4, 7 and 9 to a volume of 200 ml.
Aliquots of the stock solution were taken to obtain individual vials for every test point. Preparation was carried out under nitrogen as flushing gas, to avoid oxygen.
The vials were closed and incubated at 50 °C in a heat regulator under dark to avoid any photolytic effects.
The pH of the blank buffer solution was checked at the beginning of the test. Additionally the pH of the hydrolysis solution was measured at each test point. The temperature during the experiment was also checked at each test point.
The calibration was verified daily at the level of 117.6 mg/l by using a control calibration solution.
At each test point the hydrolysis solution was directly led to the chromatographic measurement.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

289 mg/L

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

291 mg/L

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

287 mg/L

Preliminary study:

The hydrolysis behaviour of dibutyl hydrogen phosphate was investigated at 50 °C at pH 4, pH 7 and pH 9 over a period of five days according to OECD TG 111. Dibutylphosphat is found to be stable at 50°C at all three pH-values.

Transformation products:

no

% Recovery:

101.9

pH:

4

Temp.:

50 °C

Duration:

5 d

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

97.8

pH:

7

Temp.:

50 °C

Duration:

5 d

Remarks on result:

hydrolytically stable based on preliminary test

% Recovery:

96.2

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:

According to OECD 111, a hydrolysis of less than 10 % at 50°C for 5 day corresponds to a half-life of more than 1 year at 25°C.

The overall degradation of dibutyl hydrogen phosphate observed with the determination of the content of dibutyl hydrogen phosphate at 50 °C at pH 4, 7 and 9 after 5 days is less than 10 %. Dibutyl hydrogen phosphate is therefore considered to be stable at 50 °C at pH 4, 7 and 9 and no half-life time and hydrolysis rate were calculated. Because no degradation was observed, no sterility test was performed in this case. No further tests at other temperatures are required.

Validity criteria fulfilled:

yes

Remarks:

Results of the solutions for verification of the calibration show stability of the chromatographic system. Recoveries of the test item are in the range from 97.5 % to 104.4% indicating a satisfying repeatability of the method.

Conclusions:

The substance is stable at pH 4, 7 and 9 at 50°C.

Executive summary:

The stability towards hydrolysis was investigated at pH 4, 7 and 9 at 50°C according to OECD Guideline 111 (Hydrolysis as a Function of pH). After 5 days the recoveries of dibutyl hydrogen phosphate are in the range of 97.5 % to 104.4%. Therefore, dibutyl hydrogen phosphate is regarded as hydrolytically stable, and no half-life time and hydrolysis rate were calculated.

Description of key information

The stability towards hydrolysis of dibutyl hydrogen phosphate was investigated at pH 4, 7 and 9 at 50°C according to OECD Guideline 111 (Hydrolysis as a Function of pH). After 5 days the recoveries of the substance were in the range of 97.5 % to 104.4%. The stability was monitored by HPLC analysis using MS-detection. Dibutyl hydrogen phosphate is found to be hydrolytically stable at 50°C at all three pH-values. Therefore it can be assumed that the substance is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.