Trimethylacetic anhydride

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- pH of the blank buffer solution: checked at the beginning of the test; the pH of the hydrolysis solution was measured at each test point
- The temperature during the experiment was also checked at each test point
- Suitability of the GC system: verified on every day of application
- Recovery and the repeatability of the analytical method: checked on every day of application
- The calibration was verified daily by using a control calibration solution
- The hydrolysis test solutions were analyzed by GC-FID at defined time intervals

Buffers:

- Buffer pH 4: Citric acid/NaOH/NaCl (Fluka, Order no.: 33643)
- Buffer pH 7: KH2PO4/Na2HPO4 (Fluka, Order no.: 33646)
- Buffer pH 9: Na2B4O7/HCl (Fluka, order no.: 33648) (autoclaved)

Details on test conditions:

TEST DESIGN (pH 4, 7 and 9):
I. Preparation of the hydrolysis stock solution
- A stock solution of the test item was prepared by weighing of 105.5 mg of the test item in a 10 mL measuring flask which was then filled to the mark with acetonitrile, resulting in a final concentration of 10.550 mg/mL

II. Preparation of the hydrolysis test solutions
Preparation of the hydrolysis test solutions:
- 105.5 mg of the test item were accurately weighed and dissolved to 10 mL with acetonitrile (stock solution)
- 10 mL of the tempered buffer solution was first filled into a 20 mL brown glass vial
- 100 μL of the stock solution was added into the tempered buffer solution
- Aliquots of the stock solution were taken to obtain individual vials for every test point.
- The vials were closed and incubated at 50 °C in a heat regulator under dark to avoid any photolytic effects
- At each sampling point 800 µL acetonitrile were added to 200 µL hydrolysis solution and then analysed by GC-FID

II. Calculation of hydrolysis:
- Hydrolysis had been observed and calculated using the total peak area values of the test item

III. pH determination:
- The determination was done with a pH-meter equipped with a calibrated single-rod glass electrode

IV. Sterility test:
- A plate count test according to prEN ISO 7218 (2005) was conducted at the end the hydrolysis tests

V. Solubility and test concentration:
- The test item was applied as aqueous buffer solutions (including 1 % acetonitrile) with a concentration of approx. 106 mg/L
- Clear solutions were obtained
- No further solubility test with organic solvent additives > 1% v/v was performed

Duration:

165 min

pH:

4

Temp.:

50 °C

Initial conc. measured:

100 other: %

Duration:

69 min

pH:

7

Temp.:

50 °C

Initial conc. measured:

100 other: %

Duration:

14 min

pH:

9

Temp.:

50 °C

Initial conc. measured:

100 other: %

Transformation products:

not measured

% Recovery:

10

pH:

4

Temp.:

50 °C

Duration:

165 min

Remarks on result:

other: Not stable at 50 °C

% Recovery:

9.1

pH:

7

Temp.:

50 °C

Duration:

69 min

Remarks on result:

other: Not stable at 50 °C

% Recovery:

3

pH:

9

Temp.:

50 °C

Duration:

14 min

Remarks on result:

other: Not stable at 50 °C

pH:

4

Temp.:

50 °C

DT50:

< 12 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Not stable at 50 °C

Details on results:

Due to the observed rapid degradation of the test item within minutes, an exact determination of half-life time or hydrolysis rate at pH 7 and 9 was not possible.

Quality criteria

I. Repeatability:

- Results of the solutions for verification of the peak area repeatability show stability of the chromatographic system

- Relative standard deviations of 0.2 -4 % indicate a satisfying repeatability and precision of the method applied to quantify the test item concentrations over the test duration of 5 days

II. Sensitivity:

- Regarding the chromatogram of the lowest concentration of 1.004 mg/L used for calibration, the analytical method was sufficiently sensitive to quantify test item concentrations down to 10 % or less of the initial concentration used in the hydrolysis experiment

Validity criteria fulfilled:

yes

Conclusions:

At pH 4, 7 and 9 the substance hydrolysed within hours in water at 50 °C. The estimated half-life time at pH 4 was lower than 12 hours. Due to the observed rapid degradation of the test item within minutes, an exact determination of half-life time or hydrolysis rate at pH 7 and 9 was not possible.

Executive summary:

The tests were performed according to OECD Guidelines for Testing of Chemicals, Section 1 – Physical-Chemical Properties, OECD TG 111, Council Regulation (EC) No 440/2008, Guideline Part C – Methods for the Determination of Ecotoxicity, C.7. “Abiotic Degradation: Hydrolysis as a Function of pH”. The hydrolysis behaviour of the test item was investigated at 50 °C at pH 4, 7 and 9 until less than 10 % of the initial concentration could be found. The stability was monitored by GC analysis using FID-detection. At pH 4, 7 and 9 the substance hydrolysed within hours. The estimated half-life time at pH 4 was lower than 12 hours. An exact determination of half-life time or hydrolysis rate at pH 7 and 9 was not possible due to the observed rapid degradation of the test item within minutes. Trimethylacetic anhydride can be classified as not stable at 50 °C and therefore no further tests were carried out for 5 days.

Description of key information

At pH 4, 7 and 9 the substance hydrolysed within 12 hours in water at 50 °C. The estimated half-life time at pH 4 was lower than 12 hours. Due to the observed rapid degradation of the test item within minutes, an exact determination of half-life time or hydrolysis rate at pH 7 and 9 was not possible.

Key value for chemical safety assessment

Half-life for hydrolysis:

12 h

at the temperature of:

50 °C

Additional information

"Should read: lower than 12 hours at pH 4"

Trimethylacetic anhydride can be classified as not stable at 50 °C and therefore no further tests were carried out for 5 days.