Allyl (cyclohexyloxy)acetate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

04 Mai 2016 - 08 Apr 2017

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)

Version / remarks:

2004

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)

Remarks:

Staatliches Gewerbeaufsichtsamt Hildesheim, Germany

Radiolabelling:

no

Analytical monitoring:

yes

Remarks:

UPLC-DAD

Details on sampling:

- Sampling intervals for the parent/transformation products: For the preliminary test, samples were taken at test start (0 h) and test end (120 h). For the definitive test, samples were taken at test start (0 h) and at a minimum of 10 spaced points for pH 7 and 9, normally between 10 and 90% of hydrolysis. Quantification of the major transformation products, was carried out, from retained samples of the kinetics part of the study.
- Sampling method: autosampler
- Sampling intervals/times for sterility check: Sterility of the test solutions was checked at test end by colony forming units determination with Water Plate Count Agar from additional samples of the definitive test by incubation at 36 ± 1 °C for 48 h and at 22 ± 1 °C for 72 h. As the test duration was =< 120 h for the test condition at pH 9 and 20, 30 and 50 °C, no determination of CFU was deemed necessary at these test conditions.
- Sample storage conditions before analysis: All samples were analysed as fast as possible to avoid further transformation.

Buffers:

- pH: preliminary test: 4, 7 and 9; final test: 7, 9
- Type of buffer: Buffer solutions were prepared from chemicals with analytical grade or better quality following the composition guidance given in “Küster-Thiel, Rechentafeln fur die Chemische Analytik” and the OECD Guideline No. 111, respectively, by direct weighing of the buffer components. The pH was checked to a precision of at least 0.1 at the test temperatures.
- Composition of buffer:
- Buffer solution pH 4: 0.18 g NaOH and 5.7555 g mono potassium citrate were dissolved in 500 mL double distilled water.
- Buffer solution pH 7: 3.854 g of ammonium acetate were dissolved in 500 ml double distilled water.
- Buffer solution pH 9: 0.426 g NaOH, 1.8638 g KCI and 1.5458 g H3BO3 were dissolved in 500 mL double distilled water.
- Test concentration: 800 mg/L buffer pH 4, 7 and 9 with 1% acetonitrile, respectively.

Estimation method (if used):

The quantity of the transformation products, from retained samples of the kinetics part of the study, were achieved by LC-DAD and calculated via response factor (0.7977 for transformation product #1) of the test item or external standard (transformation product #2).

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 4 mL HPLC vials (test volume: 2 mL)
- Sterilisation method: Buffers were sterilized by filtration through 0.2 µm.
- Lighting: no
- Measures taken to avoid photolytic effects: Photolytic effects were avoided by using opaque water baths.
- Measures to exclude oxygen: Buffers were purged with nitrogen for 5 min.
- Co-solvent: Acetonitrile, < 1 % (v/v)

Duration:

719 h

pH:

7

Temp.:

20 °C

Initial conc. measured:

835 mg/L

Duration:

719 h

pH:

7

Temp.:

30 °C

Initial conc. measured:

835 mg/L

Duration:

600 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

835 mg/L

Duration:

76.3 h

pH:

9

Temp.:

20 °C

Initial conc. measured:

814 mg/L

Duration:

27.9 h

pH:

9

Temp.:

30 °C

Initial conc. measured:

681 mg/L

Duration:

3.68 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

765 mg/L

Number of replicates:

Duplicates per pH value and sampling date, single injected

Preliminary study:

In the preliminary test more than 10 % of the test item was degraded after 120 h at pH 7 and 9.
- pH 4: 4.95% degradation after 120 h
- pH 7: 82.8% degradation after 120 h
- pH 9: 100% degradation after 120h

Transformation products:

yes

No.:

#1

No.:

#2

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

- Formation and decline of each transformation product during test: see field "any other information on results incl. tables"
- Pathways for transformation: The presented transformation products confirm the typical ester hydrolysis by cleavage of the ester bond.
- Other: Transformation product #2 was quantified against external standard. The calibration showed a quadratic run of the curve. The quadratic function is acceptable in view of the results. Transformation product #1 was quantified against test item calibration, taking a response factor based on the molecular weights into account. Both transformation products are major transformation products. In combination, precursor ion scans of typical fragment masses (for ionisable analytes) and evaluation of the LC-DAD analysis were performed in order to scan for other possible transformation products. No additional signals were observed.

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

0 s-1

DT50:

1 536 h

Type:

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

pH:

7

Temp.:

30 °C

Hydrolysis rate constant:

0 s-1

DT50:

850 h

Type:

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

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0 s-1

DT50:

184 h

Type:

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

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

0 s-1

DT50:

22.9 h

Type:

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

pH:

9

Temp.:

30 °C

Hydrolysis rate constant:

0 s-1

DT50:

7.05 h

Type:

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

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

0 s-1

DT50:

0.993 h

Type:

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

pH:

4

Temp.:

50 °C

Remarks on result:

hydrolytically stable based on preliminary test

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

MAJOR TRANSFORMATION PRODUCTS
- For details see field "any other informaiton on results incl. tables"

MINOR TRANSFORMATION PRODUCTS
- No minor transformation products identified.

VALIDITY CRITERIA:

- The regression graphs showed a correlation factor >= 0.8 for each test condition, confirming first order behavior.

- The test temperature did not differ by more than ± 0.5 °C, except at pH 7 and 30 °C.

- The pH values of the buffer solutions were in the range of ± 0.1 pH at test temperature.

- Sensitivity of the analytical method was sufficient to quantify concentrations of the substance at least down to 10% of the applied test item.

DETAILS ON RESULTS:

At pH 4 no significant reduction of the test item concentration was observed in the preliminary test and therefore the test item was considered as hydrolytically stable under this condition and a half-life of > 1 year could be assumed for environmental typical temperatures.

Table 1: Content of Major Transformation Products and Mass Balance at pH 7 and 9 and 20, 30 and 50 °C.

pH 7
20 °C					30°C					50°C
Hydrolysis time [h]	Transformation product #1 [mg/L]	Transformation product #2 [mg/L]	Parent Substance [mg/L]	MB [%]	Hydrolysis time [h]	Transformation product #1 [mg/L]	Transformation product #2 [mg/L]	Parent Substance [mg/L]	MB [%]	Hydrolysis time [h]	Transformation product #1 [mg/L]	Transformation product #2 [mg/L]	Parent Substance [mg/L]	MB [%]
0	0	0	846	100	0	0	0	846	100	0	0	0	846	100
5.45	0	0	877	104	5.63	0	0	797	94	2.05	0	0	833	98
23.3	0	0	890	105	23.1	8.06	0	811	96	5.77	14.4	0	801	95
75.8	8.86	0	862	102	76.3	29.5	0	758	90	22.8	53.9	13.9	713	90
166	22.9	0	846	100	166	53.7	14.5	730	92	30.9	73.8	24.3	687	91
239	29.2	17.5	847	107	239	84.3	23.8	710	93	76.6	142	41.7	544	81
336	40.3	19.5	844	108	335	106	24	623	83	165	208	51.3	359	63
407	47	18.4	683	88	407	109	26.6	565	78	239	247	63.4	227	52
506	57.2	17.8	653	84	506	145	35.6	538	78	335	282	69.4	209	53
599	84.6	18.7	705	91	599	132	35.6	458	68	406	289	77.9	148	49
719	68.7	30.1	680	92	719	153	40.6	478	73	600	339	78.9	80.2	41
pH 9
20 °C					30°C					50°C
Hydrolysis time [h]	Transformation product #1 [mg/L]	Transformation product #2 [mg/L]	Parent Substance [mg/L]	MB [%]	Hydrolysis time [h]	Transformation product #1 [mg/L]	Transformation product #2 [mg/L]	Parent Substance [mg/L]	MB [%]	Hydrolysis time [h]	Transformation product #1 [mg/L]	Transformation product #2 [mg/L]	Parent Substance [mg/L]	MB [%]
0	0	0	724	100	0	0	0	716	100	0	0	0	724	100
5.45	39.1	19.9	727	110	5.63	16	8.5	775	112	2.05	58	31.8	642	104
23.3	86.7	49.2	675	116	23.1	47.5	26.2	688	109	5.77	107	62.1	584	110
75.8	205	127	455	123	76.3	72.9	53.5	589	112	22.8	141	90	482	109
166	230	140	431	125	166	113	69.1	566	112	30.9	178	109	385	105
239	233	153	302	114	239	143	89.1	490	140	76.6	228	144	268	105
336	226	143	351	116	335	176	99.1	422	106	165	248	154	220	103
407	247	152	270	109	407	193	123	377	189	239	162	151	177	96
506	234	153	358	122	506	211	126	299	102	335	292	174	124	99
599	293	182	174	110	599	319	195	70.7	103	406	314	192	117	107
719	362	225	70.6	116	719	329	207	37.8	104	600	343	196	34.7	97

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Conclusions:

The test item showed a slow hydrolysis rate (t1/2 > 30 d) for pH 7 at 20 and 30 °C, a moderate hydrolysis rate (2.4 h =< t1/2 =< 30 d) for pH 7 at 50 °C and for pH 9 at 20 and 30 °C and a fast hydrolysis rate at pH 9 at 50 °C, with the higher half-lives at acidic conditions. At pH 4 no significant reduction of the test item concentration was observed in the preliminary test and therefore the test item was considered as hydrolytically stable under this condition and a half-life of > 1 year was assumed for environmental typical temperatures. Two major transformation products were found confirming the typical ester hydrolysis by cleavage of the ester bond.

Executive summary:

The hydrolysis potential of the substance as a function of pH was determined according to the OECD Guideline 111, the Council Regulation (EC) No. 440/2008, Method C.7 and GLP. The hydrolysis determination was performed via LC-DAD on a reversed phase analytical column using the test item as external standard. Based on the results of a preliminary test the definitive test was conducted with a test item concentration of 800 mg/L in buffer solutions of pH 7 and 9 containing 1% acetonitrile at temperatures of 20, 30 and 50 °C, respectively. Samples were taken at test start and at 9 to 10 spaced points until test end.

The substance has a slow hydrolysis rate (t1/2 > 30 d) at pH 7 and 20 - 30 °C, a moderate hydrolysis rate (2.4 h ≤ t1/2 ≤ 30 d) at pH 7 and 50 °C as well as at pH 9 and 20 - 30 °C while a fast hydrolysis rate was found at pH 9 and 50 °C (t1/2 = 12. h). At pH 4 no significant reduction of the test item concentration was observed and the test item was considered as hydrolytically stable at this pH and environmental typical temperatures. Two major transformation products were determined confirming the typical ester hydrolysis by cleavage of the ester bond.

Description of key information

Half-life 1536 h at pH 7 and 20°C

Key value for chemical safety assessment

Half-life for hydrolysis:

1 536 h

at the temperature of:

20 °C

Additional information

The hydrolysis potential of the substance as a function of pH was determined according to the OECD Guideline 111, the Council Regulation (EC) No. 440/2008, Method C.7 and GLP. The hydrolysis determination was performed via LC-DAD on a reversed phase analytical column using the test item as external standard. Based on the results of a preliminary test the definitive test was conducted with a test item concentration of 800 mg/L in buffer solutions of pH 7 and 9 containing 1% acetonitrile at temperatures of 20, 30 and 50 °C, respectively. Samples were taken at test start and at 9 to 10 spaced points until test end.

The substance is characterized by a slow hydrolysis rate (t1/2 > 30 d) at pH 7 and 20 - 30 °C, a moderate hydrolysis rate (2.4 h ≤ t1/2 ≤ 30 d) at pH 7 and 50 °C as well as at pH 9 and 20 - 30 °C while a fast hydrolysis rate was found at pH 9 and 50 °C (t1/2 = 12. h). At pH 4 no significant reduction of the test item concentration was observed and the test item was considered as hydrolytically stable at this pH and environmental typical temperatures. Two major transformation products were determined confirming the typical ester hydrolysis by cleavage of the ester bond.