Glycerol, propoxylated, esters with acrylic acid, reaction products with diethylamine

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2015-07-09 to 2017-02-23

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 sampling:

When the test item is solubilised in buffer solutions, a more or less rapid degradation was observed leading to the predominant formation of DEAPA as shown on the GC/MS chromatographic profiles. As the test item is analysed with the help of a GC/MS analytical technique which needs around 35 minutes per samples while UPLC/MS (used for DEAPA concentrations determination) needs around 3 minutes, the test item concentrations may not be reliable. For this reason and in accordance with the study monitor, it was decided to consider the test item degradation product concentrations (DEAPA) rather than the test item concentrations.

Buffers:

PRELIMINARY TEST
The preliminary test was carried at four pH values: 1.2, 4, 7 and 9. The corresponding buffer solutions were prepared using reagent grade chemicals and ultra-pure water as follows:
- pH 1.2: potassium chloride (3.7276 g) was mixed with HCl (64.5 ml) and made to volume (1L) with ultra-pure water. The pH was measured as 1.2.
- pH 4: potassium phthalate monobasic (10.211 g) was mixed with sodium hydroxide (0.4 mL) and made to volume (1L) with ultra-pure water. The pH was measured as 4.0.
- pH 7: potassium dihydrogen phosphate (6.804 g) was mixed with sodium hydroxide (29.63 mL) and made to volume (1L) with ultra-pure water. The pH was measured as 7.0.
- pH 9: boric acid (3.0915 g) and potassium chloride (3.7275 g) were mixed with sodium hydroxide (21.3 mL) and made to volume (1L) with ultra-pure water. The pH was measured as 9.0.

DEFINITIVE TEST
The definitive test was carried at 2 pH values: 7 and 9. The corresponding buffer solutions were prepared using reagent grade chemicals and ultra-pure water as follows:
- pH 7: potassium dihydrogen phosphate (13.6081 g) was mixed with sodium hydroxide (59.3 mL) and made to volume (2L) with ultra-pure water. The pH was measured as 7.03.
- pH 9: boric acid (6.1830 g) and potassium chloride (7.4550 g) were mixed with sodium hydroxide (42.6 mL) and made to volume (2L) with ultra-pure water. The pH was measured as 9.00.

Details on test conditions:

PRELIMINARY TEST
Temperatures were recorded as follows:
- pH 1.2 at 37°C: range from 36.1 to 36.3°C (mean: 36.2)
- pH 4, 7 and 9 at 50°C: range from 49.6 to 49.8°C (mean: 49.7)

DEFINITIVE TEST
Temperatures were recorded as follows:
- 15°C: range from 15.1 to 15.3°C (mean: 15.1)
- 37°C: range from 37.0 to 37.1°C (mean: 37.1)
- 50°C: range from 49.2 to 49.4°C (mean: 49.3)

Number of replicates:

Two replicates for each tested temperature at each pH

Negative controls:

yes

Remarks:

Buffer control

Preliminary study:

Only DEAPA concentrations should be considered as the test item concentrations may not be reliable due to its quick degradation and analysis time with GC/MS.

In addition, regarding results obtained with the replicates 2 (which correspond to the theoretical loading rates of 25 g/L) at pH 7 and 9, DEAPA was already determined at its highest concentration at Day 0. Its concentration also slightly increased after 5 days. The loading rate being probably too high, replicates 2 results were disregarded.

At pH 1.2 and 4, DEAPA was neither detected at Day 0 nor Day 5. Furthermore, recoveries of test item remaining did not changed by more than 10% between T0 and T5 days. The test item was thus considered to be hydrolytically stable at these pH.

The test item being stable in water at pH 1.2 and 4, it was decided to perform the definitive test at pH 7 and 9 in accordance with the Study Monitor.

Transformation products:

yes

No.:

#1

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.037 h-1

DT50:

18.68 h

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.22 h-1

DT50:

3.16 h

pH:

7

Temp.:

15 °C

Hydrolysis rate constant:

0.012 h-1

DT50:

59 h

pH:

7

Temp.:

37 °C

Hydrolysis rate constant:

0.064 h-1

DT50:

10.82 h

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.046 h-1

DT50:

15.2 h

pH:

9

Temp.:

15 °C

Hydrolysis rate constant:

0.332 h-1

DT50:

2.09 h

pH:

9

Temp.:

37 °C

Hydrolysis rate constant:

0.105 h-1

DT50:

6.63 h

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

1.383 h-1

DT50:

0.5 h

pH = 7

The half-life of the test item at pH 7 was determined to be as follows:

15°C: 59.0 hours / 2.5 days

37°C: 10.82 hours / 0.5 days

50°C: 15.20 hours / 0.6 days

The value of kcalc at 25°C was obtained by using the Arrhenius equation: Ln (K) = f(1/T)

15°C: Kobs = 0.012, Ln(Kobs) = -4.444, 1/T = 0.0035

37°C: Kobs = 0.064, Ln(Kobs) = -2.749, 1/T = 0.0032

50°C: Kobs = 0.046, Ln(Kobs) = -3.088, 1/T = 0.0031

25°C: Kcalc = 0.0371, Ln(Kcalc) = -3.2939, 1/T = 0.0034

The half-life of the test item at pH 7 and 25°C was determined to be 18.68 hours (i.e. 0.8 days).

However, these results are of low reliability as shown by linear regression of the scatterplots with log-transformed data of the substances concentrations versus time. Indeed, the determination coefficients of the regressions are low. Therefore, these results should be considered with caution.

pH = 9

The half-life of the test item at pH 9 was determined to be as follows:

15°C: 2.09 hours / 0.1 days

37°C: 6.63 hours / 0.3 days

50°C: 0.5 hours / 0.0 days

 

The value of kcalc at 25°C was obtained by using the Arrhenius equation: Ln (K) = f(1/T)

15°C: Kobs = 0.332, Ln(Kobs) = -1.104, 1/T = 0.0035

37°C: Kobs = 0.105, Ln(Kobs) = -2.258, 1/T = 0.0032

50°C: Kobs = 1.383, Ln(Kobs) = -0.325, 1/T = 0.0031

25°C: Kcalc = 0.2195, Ln(Kcalc) = -1.5165, 1/T = 0.0034

 

The half-life of the test item at pH 9 and 25°C was determined to be 0.1 days (i.e. 3.16 hours).

 

However, these results are of low reliability as shown by linear regression of the scatterplots with log-transformed data of the substances concentrations versus time. Indeed, the determination coefficients of the regressions are low. Therefore, these results should be considered with caution.

Sterility Check

The last analysed samples at pH 9 were checked for sterility with the help of a microscopic observation: no sample contained microorganisms were observed.

Executive summary:

The objective of this study was to determine the rate of hydrolysis of the test item as a function of pH according to the OECD 111 Guideline.

For analytical reasons, the test item hydrolysis was studied through the formation of its major metabolite DEAPA.

The hydrolysis was firstly assessed in aqueous buffers at pH 1.2, 4, 7 and 9 at 50°C ± 0.5. DEAPA being neither analytically detected at Day 0 nor Day 5 at pH 1.2 and 4, the test item was not considered as hydrolytically unstable at these pH values.

The definitive test was thus conducted at pH 7 and 9 (15, 37 and 50°C):

¿ The half-life of the test item at pH 7.0 and 25°C was determined to be 18.68 hours.

¿ The half-life of the test item at pH 9.0 and 25°C was determined to be 3.16 hours.

However, these results are of low reliability as shown by linear regression of the scatterplots with log-transformed data of the substances concentrations versus time. Indeed, the determination coefficients of the regressions are low. Therefore, these results should be considered with caution.

Description of key information

A hydrolysis as a function of pH study was conducted according to the OECD Test Guideline 111 with Glycerol, propoxylated, esters with acrylic acid, reaction products with diethylamine (CAS 162492-10-6).

For analytical reasons, the test item hydrolysis was studied through the formation of its major metabolite DEAPA (CAS 6972-41-4).

The test item was considered hydrolytically stable at pH 1.2 and 4. It was found to be hydrolytically unstable at pH 7 and 9, with half-lives of 18.68 and 3.16 hours, respectively, at 25°C.