N-[2,5-dichloro-4-(1,1,2,3,3,3-hexafluoropropoxy)-phenyl-aminocarbonyl]-2,6-difluorobenzamide

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

3 May 1990 to 8 May 1992

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:

12 May 1981

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

other: EPA 161-1

Version / remarks:

18 October 1982

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

Except for pH 5, 7 and 9 at 25°C one test tube was taken for analysis at each sampling time. Under conditions where only little degradation of the test compound was observed samples were taken up to 30 days. For all other experiments samples were taken up to at least one half-life.

Buffers:

pH = 1 neutralised with 1N NaOH
pH = 5 neutralised with 0.1N NaOH
pH = 9 neutralised with 0.1N HCL
pH = 13 neutralised with 1N HCL

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: Tightly closed, brown test tubes of 20 mL volume
- Sterilisation method: Prior to the treatment all glassware, test tubes and treatment devices were sterilised by autoclaving for 15 to 30 minutes at about 120°C. Buffer solutions were prepared from the test facility standard solutions which were adequately diluted to a molarity of about 0.01M with boiled, distilled water. After dilution the pH was measured and the buffers sterilised by filtration. Filling of test tubes and treatment was performed under aseptic conditions.
- Lighting: Incubation and handling of samples was performed under a minimum of light exposure.
- Details on test procedure: During exposure the tubes were shaken at about 200 rpm at temperatures of 25, 50 or 70°C.
- If no traps were used, is the test system closed/open: Closed

TEST MEDIUM
- Volume used/treatment: 5 mL buffer and 50 µL of corresponding stock solution
- Preparation of test medium:
> Substance 1 (Batch: LE-78.3A): The test substance (about 2.4 mg) was dissolved in 10 mL acetone followed by three dilutions (50 µL in 5.0 mL acetone) for measurement of radioactivity and purity of the test compound. From each dilution a subsample of 50 µL was removed and its radioactivity determined by LSC. The amount of test substance was calculated to be 2.3863 mg using the specific radioactivity of 51.35 µCi/mg.
> Substance 2 (Batch: 068F9249): The test substance (about 2 mg) was dissolved in 10 mL acetone followed by three dilutions (50 pl in 5.0 mL acetone) for measurement of radioactivity and purity of the test compound. From each dilution a subsample of 50 µL was removed and its radioactivity determined by LSC. The amount of test substance was calculated to be 1.984 mg using the corrected, specific radioactivity of as 115.20 µCi/mg determined analytically.
> Substance 3 (068F9249-1): The test substance (about 1 mg) was dissolved in 5 mL acetone followed by three dilutions (50 µL in 5 mL acetone) for measurement of radioactivity and purity of the test compound. From each dilution a subsample of 50 µL was removed and its radioactivity determined by LSC. The amount of test substance was calculated to be 0.9511 mg using the specific radioactivity of 102.43µCi/mg as determined analytically.
- Treatment of Test Samples: To each test tube 5.0 mL buffer were given and then 50 µL of the corresponding stock solution added by means of a 100 µL Hamilton syringe. By this procedure the following concentration of the test compound were obtained:
Radiolabelled test substance 1 (Batch: Le-78.3A): 0.0119 mg/5mL
Radiolabelled test substance 2 (Batch: 068F9249): 0.0099 mg/5mL
Radiolabelled test substance 3 (Batch: 068F9249-1): 0.0087 mg/5mL

Initial conc. measured:

>= 0.009 - <= 0.012 other: mg/5mL

Remarks:

test temperature: 25, 50 and 70°C; test pH: 1, 5, 7, 9 and 13

Number of replicates:

See Table 1 in 'Any other information on materials and methods incl. tables'.

Positive controls:

no

Negative controls:

no

Statistical methods:

Rate constants at experimental Temperatures:
Experimental data were analysed assuming pseudo-first order reaction kinetics.
-dx/dt = k1 *(a-x) or (a/a-x) = k1 *t
where x denotes the amount of reactant A consumed per unit volume, a in the initial
concentration of the test substance, a-x the remaining concentration of the test substance at time t and k1 in the rate constant of the parent at time t. The rate constants were calculated via linear regression.

Half-lives:
Half-lives were calculated according the equation t0.5 = Ln2/k1

Rate constants at other Temperatures:
Rate constants and half-lives others than those experimentally determined were calculated using the Arrhenius equation
K = A*e^-(Ea/RT) or Lnk=-Ea/R*1/T+Ln A
Where A is the frequency factor (/s), Ea the activation energy (J/mole), R the gas constant (8.3144 J*/mole/K) and T the absolute temperature (K). The figures for Ea, and A were obtained by correlation of the experimentally determined rate constants k with the reciprocal temperatures.

Transformation products:

not specified

Remarks:

M1, M2, M3, M4, M5, M6, M7 and M8

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

An overview of the results is provided in Table 2 - Table 3 in 'Any other information on results incl.tables'.
- Formation of Degradates and Identification (Dichlorophenylring-Iabelled test substance): Besides minor degradates and radioactive fraction, 5 degradates were predominantly formed under alkaline conditions at elevated temperatures, i.e. M6, M2, M4, M5 and unknown1. At pH 9 and 70°0, degradates M6 and M2 were terminal degradates reaching after 120 hours concentrations of 60.9, and 15.4%, respectively. M4 represented a transient degradate reaching with 29.9% its highest concentration after 24 hours and at the end of the study M4 accounted for 9.0% only. At pH 13 (70°C) degradates M6, M2, M4 and M3 reached their highest concentrations with 21.8, 6.1, 18.2 and 19.1% after 2 (M6,M2 and M4) and after 32 hours (M3), respectively. At the end of the study their corresponding amounts were 0 and 15.9%. Only M5 was found to be a terminal degradate amounting to 51.3 after 96 hours of exposure.
- Formation of Degradates and Identification (Difluorophenylring-Iabelled test substance): Besides minor degradate, 6 degradates were predominantly formed under neutral (70°C) and alkaline conditions at elevated temperatures, i. e. M2, M1, unknown 1, M8 and M7. At pH 7 and 70°C M2, M8 and M7 were formed amounting at the end of the study to 13.7, 31.6 and 66.0 %, respectively. The pattern of degradates was very similar at pH 9 at 60°C and 70°C. At pH 13 at 50 and 70°C two additional transient and minor degradates were formed (M1 and unknown 1) accounting at 70°C at highest for 5.6 - 2.2%, and at the end of the study for 1.5 and 0%. Degradates M2 and M3 were under the same conditions found also to be transient, i.e. their corresponding amounts were after 2.6 hours 3.2 and 7.2%. Only degradates M8 and M7 were terminal degradates amounting to 48.9 and 39.2%, respectively.

% Recovery:

>= 91.46 - <= 100

Duration:

>= 1 - <= 30 d

Remarks on result:

other: Dichlorophenyl–labelled; on the last sampling day of each test conditions

% Recovery:

>= 92.78 - <= 100

Duration:

>= 0.1 - <= 30 d

Remarks on result:

other: Difluorophenyl–labelled; on the last sampling day of each test conditions

Key result

pH:

7

Temp.:

25 °C

DT50:

> 30 d

Type:

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

Remarks on result:

other: dichlorophenyl–labelled; DT50 >> 720 h

Key result

pH:

7

Temp.:

25 °C

DT50:

> 30 d

Type:

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

Remarks on result:

other: difluorophenyl –labelled; DT50 >> 720 h

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0 s-1

DT50:

169.4 d

Type:

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

Remarks on result:

other: dichlorophenyl–labelled

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0 s-1

DT50:

77.43 d

Type:

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

Remarks on result:

other: difluorophenyl –labelled

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

377.6 d

Type:

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

Remarks on result:

other: dichlorophenyl–labelled

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

646.3 d

Type:

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

Remarks on result:

other: difluorophenyl –labelled

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

0 s-1

DT50:

7.7 d

Type:

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

Remarks on result:

other: dichlorophenyl–labelled

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

0 s-1

DT50:

1.7 d

Remarks on result:

other: difluorophenyl –labelled

pH:

5

Temp.:

25 °C

DT50:

> 30 d

Type:

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

Remarks on result:

other: dichlorophenyl–labelled; DT50 >> 720 h

pH:

5

Temp.:

25 °C

DT50:

> 30 d

Type:

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

Remarks on result:

other: difluorophenyl–labelled; DT50 >> 720 h

pH:

5

Temp.:

70 °C

DT50:

> 30 d

Type:

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

Remarks on result:

other: dichlorophenyl–labelled; DT50 >> 720 h

Details on results:

An overview of the results is provided in Table 2 - Table 4 in 'Any other information on results incl.tables'.
- Recovery and Rate of Degradation (Dichlorophenylring-Iabelled test substance): The recovery of radioactivity was, on average, for all samples 98.8 ± 1.9%. Practically no of the parent compound was observed under acidic conditions (pH 1 and 5) up to a temperature of 70 degrees centigrade, i.e. the half-lives were >> 30 days. At pH 7 half-lives were >> 30 days, 169 days and 130.5 hours at 25, 50 and 70°C, respectively. Only under alkaline conditions a more rapid degradation of the test substance was observed. At pH 9 the half-lives were 378, 7.7 days and 4 hours at 25, 50 and 70°C, respectively. At pH 13 the corresponding half-lives were 39.6, 3.5 and 0.3 hours. Calculated half-lives for 20°C were 1222 and 3.5 days for pH 9 and 13, respectively.
- Recovery and Rate of Degradation (Difluorophenylring-Iabelled test substance): The recovery of was, on average, for all samples 98.0 ± 2.1%. Due to the results obtained with the test substance no hydrolysis was performed at pH 1. At pH 5 the degradation rate was only followed at 25°C yielding again a half-life >> 30 days. At pH 7 half-lives were >> 30 days, 77.4 days and 45.7 hours at 25, 50 and 70°C, respectively. Again, under alkaline conditions a more rapid degradation of the test substance was observed. At pH 9 the half-lives were 646, 1.7 days and 1.9 hours at 25, 50 and 70°C. respectively. At pH 13 the corresponding half-lives were 30.3, 2.7 and 0.3 hours. Calculated half-lives for 20°C were 68.2 and 2.4 days for pH 9 and 13, respectively.

Table 2. Hydrolysis of the test substance (Dichlorophenylring-Iabelled)

a) At pH 1 and 70 ˚C incubation temperature (values given in % of radioactivity applied.)

Time (hrs.)	Parent substance	M6	M2	NA	Recovery
0	99.71	0.00	0.00	0.29	100.00
4	96.76	0.00	0.00	0.27	97.03
7	99.50	1.72	0.00	0.27	101.49
24	91.43	0.92	0.00	0.32	92.67
48	96.24	0.00	0.00	0.36	96.60
72	94.00	1.36	1.07	0.39	97.79
96	97.95	1.90	0.00	0.38	100.23
120	98.63	1.91	0.00	0.42	100.96
168	97.71	2.40	0.00	0.46	100.57

NA = Radioactivity not analysed

b) At pH 5 (given in % of radioactivity applied.) 

25 ˚C			70 ˚C
Time (days)	Parent substance	recovery	Time (hrs.)	Parent substance	M6	NA	Recovery
0	99.46	99.46	0	99.50	0.00	0.50	100.00
2	98.30	98.30	24	95.73	1.26	0.57	97.56
3	97.44	97.44	48	92.59	2.37	0.58	95.54
6	97.67	97.67	72	95.23	2.54	0.66	98.43
8	99.43	99.48	96	90.13	2.41	0.58	93.12
10	100.07	100.07	120	95.39	3.05	0.65	99.09
13	99.24	99.24	168	95.83	2.76	0.72	99.31
14	99.41	99.41	216	92.88	4.48	0.75	98.11
16	99.43	99.43	250	93.02	4.38	0.72	98.12
17	97.98	97.98
20	100.28	100.28
22	99.69	99.69
23	97.71	97.71
25	95.89	95.89*
28	100.52	100.52*
30	97.75	97.75

* = only one sample

NA = Radioactivity not analysed

at 25 ˚C values represent mean of duplicate samples

 

c) At pH 7 (given in % of radioactivity applied.)

25 ˚C			50˚C						70˚C
Time (days)	Parent substance	recovery	Time (hours)	Parent substance	M6	M2	M4	Recovery	Time (hours)	Parent substance	M6	M2	M4	Recovery
0	100.01	100.01	0	100.94	0.00	0.00	0.00	100.94	0	99.27	0.00	0.00	0.73	100.00
2	99.33	99.33	24	99.98	0.00	0.00	0.00	99.98	7	87.07	2.79	1.21	0.84	93.96
3	100.59	100.59	72	99.95				99.95	24	86.64	5.71	2.36	0.95	99.40
6	99.85	99.85	120	100.87	0.00	0.00	0.00	100.87	32	84.11	8.09	2.37	1.02	99.63
8	101.19	101.19	216	99.75	0.00	0.00	0.00	99.75	48	79.25	10.91	3.37	0.95	100.13
10	97.59	97.59	336	95.62	2.43	0.00	3.14	101.19	72	69.84	17.63	4.63	1.15	99.65
13	98.63	98.63	432	93.92	2.37	0.00	2.87	98.66	96	59.04	24.73	5.86	1.12	98.86
14	97.22	97.22	438	92.08	2.24		3.22	97.54	120	49.31	28.92	8.90	1.20	96.95
16	98.44	98.44	529	94.45	2.91	0.00	3.11	100.47	168	55.71	27.48	6.87	1.07	96.47
17	97.22	97.22	749	89.01	3.14	1.57	4.52	98.24
20	99.74	99.74
22	98.47	98.47
23	99.08	99.08
25	97.24	97.24
28	98.98	98.98
30	98.42	98.42

at 25 ˚C values represent mean of duplicate samples

 

d) At pH 9 (values given in % of radioactivity applied.) 

25˚C					50˚C						70˚C
Time (days)	Parent Substance	M6	M4	Recovery	Time (hours)	Parent substance	M6	M2	M4	Recovery	Time (hours)	Parent substance	M6	M2	M4	RF	NA	Recovery
0	99.7	0	0	99.70	0	101.04	0.00	0.00	0.00	101.04	0	99.12	0.00	0.00	0.00	0.00	0.88	100.00
2	98.68	0	0	98.68	4	97.07	0.00	0.00	3.42	100.49	2	78.16	11.27	4.35	10.08	0.00	1.12	99.98
3	99.07	0	0	99.07	6	96.58	3.07	0.00	2.77	102.42	4	46.99	24.14	9.16	18.22	0.00	1.22	99.73
6	97.81	0	1.30	99.11	8	96.96	1.42	0.00	3.04	101.42	7	30.30	33.56	10.76	24.08	0.00	1.38	100.08
8	96.75	0	1.37	98.12	24	87.59	5.15	2.02	6.16	100.92	24	10.50	46.74	14.97	24.98	0.00	1.77	98.96
10	96.21	0	2.62	98.83	32	85.74	5.47	2.33	7.80	101.34	48	7.29	53.11	14.67	13.68	1.26	2.25	92.26
13	96.65	0	1.58	98.23	48	81.94	6.16	3.63	9.18	100.91	72	8.75	49.03	16.09	19.16	0.00	1.80	94.83
14	98.98	0	0	98.98	70	71.02	9.53	4.01	15.75	100.31	96	10.95	51.62	15.75	10.68	0.00	2.09	91.09
16	97.27	0	1.54	98.81	78	68.86	9.28	5.95	16.74	100.83	120	1.77	60.94	15.35	8.96	1.69	2.75	91.46
17	94.68	0	1.38	96.06	102	60.83	13.83	5.59	17.86	98.11
20	94.12	0	3.47	97.59	150	57.85	15.05	5.96	18.86	97.72
22	96.77	0	2.74	99.51	174	53.47	15.99	7.36	21.29	98.11
23	96.04	0	2.39	98.43
25	93.86	0	3.06	96.91
28	94.46	0	3.47	97.93
30	93.47	1.77	3.87	99.10

 RF = Radioactive Fraction

NA = Not Analysed

e) At pH 13 (values given in % of radioactivity applied.)

25 ˚C						50 ˚C
Time (hours)	Parent substance	M6	M2	M4	Recovery	Time (hours)	Parent substance	M6	M2	M4	M3	Unknown 1	Unknown 2	Recovery
0	100.79	0.00	0.00	0.00	100.79	0.00	101.09	0.00	0.00	0.00	0.00	0.00	0.00	101.09
1	95.99	0.00	0.00	3.70	99.68	0.22	92.42	0.00	0.00	4.97	0.00	0.00	0.00	97.39
2	93.12	0.00	0.00	5.79	98.91	0.50	91.22	3.87	0.00	6.72	0.00	0.00	0.00	101.81
3	91.89	0.00	0.00	7.08	98.97	0.75	88.81	0.00	3.17	10.22	0.00	0.00	0.00	102.20
4	90.98	0.86	0.00	8.27	100.10	1.00	76.40	0.00	4.84	15.42	0.00	0.00	2.17	98.83
6	86.50	1.00	0.00	12.56	100.05	1.25	75.75	2.36	3.64	15.27	0.00	0.00	1.48	98.50
8	85.50	0.00	0.00	14.58	100.07	1.50	63.97	9.01	3.44	19.13	3.75	0.00	1.92	101.22
14	78.04	0.00	1.25	20.64	99.92	2.00	59.28	9.43	3.81	23.07	2.81	0.00	1.91	100.31
18	68.57	2.15	0.00	28.69	99.40	3.00	59.99	8.22	4.26	22.97	2.43	0.00	1.09	99.01
24	65.64	4.93	0.00	29.87	100.44	4.00	45.26	3.71	8.68	33.85	2.93	3.12	0.00	97.55
						5.00	38.31	5.08	7.82	36.65	2.64	7.23	0.00	97.73
						6.00	30.67	1.84	9.41	38.72	4.76	11.64	0.00	97.04
						7.00	22.99	3.68	8. 96	45.97	3.78	14.13	0.00	99.51
						8.00	19.52	3.81	8.69	43.82	4.39	17.38	0.00	97.61

  Unknown 1 represents a fraction of radioactivity containing up to 6 metabolites

f) continue: At pH 13 and 70 ˚C (values given in % of radioactivity applied.)

Time (hours)	Parent substance	M6	M2	M4	M3	Unknown 1	Unknown 2	Recovery
0	88.05	2.43	2.04	4.77	0.00	0.00	0.00	100.00
2	3.41	21.77	6.09	18.21	18.77	13.67	14.23	101.05
4	0.01	15.47	2.26	9.46	19.75	15.63	36.98	99.56
7	1.83	7.31	1.44	3.09	28.25	17.77	39.84	99.53
24	0.00	0.00	0.00	0.00	38.51	17.74	41.74	97.99
32	0.00	0.00	0.00	0.00	42.27	19.05	33.24	99.22
48	0.00	0.00	0.00	0.00	43.48	18.97	34.83	97.28
72	0.00	0.00	0.00	0.00	45.62	16.75	33.88	96.25
96	0.00	0.00	0.00	0.00	51.27	15.92	30.47	97.66

Unknown 1 represents a fraction of radioactivity containing up to 6 metabolites

Table 3. Hydrolysis of the test substance (Difluorophenylring-Iabelled)

a) At pH 5 (given in % of radioactivity applied.)

25 ˚C
Time (days)	Parent substance	recovery
0	98.59	98.59
2	97.03	97.03
3	96.44	96.44
5	97.34	97.34
8	95.87	95.87
10	95.93	95.93
11	97.39	97.39
14	98.33	98.33
16	96.76	96.76
18	97.22	97.22
21	97.90	97.90
22	97.46	97.46
24	96.19	96.19
25	96.25	96.25
28	93.23	93.23
30	97.30	97.30

at 25 ˚C values represent mean of duplicate samples

b) At pH 7 (given in % of radioactivity applied.)

25˚C			50˚C						70˚C
Time (days)	Parent substance	recovery	Time (hours)	Parent substance	M2	M8	M7	Recovery	Time (hours)	Parent substance	M2	M8	M7	Unknown 3	Recovery
0	98.39	98.39	0	97.27	0.00	0.00	0.00	97.27	0	100.47	0.00	0.00	0.00	0.00	100.47
2	97.91	97.91	96	95.67	0.00	0.00	0.00	95.67	24	67.24	4.40	9.40	18.81	0.70	100.05
3	95.50	95.50	192	88.42	0.00	3.88	2.37	94.67	48	65.00	5.27	10.24	18.88	0.00	99.39
5	98.49	98.49	288	84.58	0.00	4.90	3.05	92.53	72	49.08	6.35	15.87	27.86	0.00	99.16
8	98.98	98.98	384	83.38	0.00	6.28	4.03	93.69	96	26.73	9.38	21.94	41.69	0.00	99.74
10	100.01	100.01	480	82.29	1.44	7.11	5.18	96.02	120	14.48	11.87	27.26	46.97	0.00	100.58
11	99.27	99.27	552	77.98	1.85	7.30	5.27	92.40	168	0.00	11.29	31.85	57.22	0.00	99.86
14	98.48	98.48	672	75.90	1.51	9.23	7.53	94.17	192	0.00	13.78	31.47	56.02	0.00	100.22
16	98.52	98.52	720	74.13	2.41	9.37	6.87	92.78
18	97.14	97.14
21	99.81	99.81
22	98.50	98.50
24	97.54	97.54
25	95.21	95.21
28	88.68	88.68
30	99.85	99.85

at 25 ˚C values represent mean of duplicate samples

c) At pH 9 (given in % of radioactivity applied.)

25˚C				50˚C						70˚C
Time (hours)	Parent substance	M8	recovery	Time (hours)	Parent substance	M2	M8	M7	Recovery	Time (hours)	Parent substance	M2	M3	M8	M7	Recovery
0	98.81	0.00	98.81	0	98.46	0.00	0.00	0.00	98.46	0	99.97	0.00	0.00	0.00	0.00	99.97
2	97.44	0.00	97.44	24	70.40	3.43	13.63	10.59	98.05	2	21.81	11.25	0.00	24.72	42.71	100.49
3	98.03	0.00	98.03	48	56.98	4.67	21.54	16.08	99.27	4	17.33	11.99	0.00	25.69	45.74	100.75
5	96.93	0.00	96.93	72	33.42	7.47	32.63	24.77	98.29	24	0.00	15.08	0.00	30.40	52.54	100.65
8	96.51	0.00	96.51	96	18.63	8.82	41.33	30.33	99.11	48	0.00	14.40	0.00	29.57	55.24	99.89
10	97.66	0.00	97.66	120	24.05	7.89	39.13	27.50	98.57	72	0.00	14.57	0.00	32.29	53.29	99.98
11	98.27	0.00	98.27	144	18.86	9.38	40.29	30.22	98.75	96	0.00	12.97	1.77	30.76	55.18	100.51
14	95.66	0.78	96.44	168	7.83	10.89	45.95	84.86	99.03	120	0.00	12.43	1.29	31.84	51.69	98.27
16	96.44	0.00	96.44	192	14.65	11.01	41.50	31.17	98.33
18	97.31	0.00	97.31	216	14.50	11.15	39.55	83.44	98.64
21	96.32	2.62	98.94
22	96.43	1.06	97.49
24	96.49	0.97	97.46
25	95.87	1.21	97.08
28	93.42	3.79	97.21
30	93.94	3.11	97.05

at 25 ˚C values represent mean of duplicate samples

d) At pH 13 (given in % of radioactivity applied.)

25˚C							50˚C
Time (hours)	Parent substance	M2	M1	M8	M7	Recovery	Time (hours)	Parent substance	M2	M1	M3	M8	M7	Unknown 4	Recovery
0	97.66	0.00	0.00	0.00	0.00	97.66	0	98.12	0.00	0.00	0.00	0.00	0.00	0.00	98.12
1	95.35	0.00	0.00	2.45	0.00	97.80	1	74.09	1.98	2.47	0.00	12.85	5.83	1.58	98.80
2	94.77	0.00	0.00	4.00	0.00	98.77	2	57.37	3.85	2.47	0.00	24.49	9.28	1.28	98.74
3	92.09	0.00	0.00	5.47	0.00	97.55	3	42.25	4.57	3.48	0.00	33.70	14.42	0.99	99.41
4	90.09	0.00	0.00	7.05	0.79	97.92	4	33.66	5.16	4.57	0.00	40.50	14.79	0.60	99.28
6	85.62	0.00	0.54	9.39	1.75	97.29	5	27.58	5.78	4.28	1.29	43.92	16.73	0.00	99.58
8	80.71	0.69	0.72	13.17	1.90	97.18	6	20.60	5.77	4.18	1.29	48.37	18.51	0.80	99.52
10	78.99	0.64	0.00	15.62	2.05	97.30	7	15.02	5.53	3.66	1.88	52.68	20.06	0.00	98.83
14	68.10	2.29	0.92	22.09	3.69	97.08	8	13.24	5.14	3.66	1.68	54.56	20.56	0.00	98.84
18	62.16	1.57	1.67	25.60	4.20	95.19
24	57.94	1.42	2.41	28.95	3.74	94.46

at 25 ˚C values represent mean of duplicate samples

e) At pH 13 at 70˚C (given in % of radioactivity applied.)

Time (hours)	Parent substance	M2	M1	M3	M8	M7	Unknown 4	Recovery
0.00	97.67	0.00	0.00	0.00	0.00	0.00	2.20	99.87
0.25	55.53	4.19	4.09	0.00	18.04	16.35	1.50	99.70
0.50	28.31	6.35	5.64	1.31	28.61	29.11	1.41	100.74
0.75	16.42	7.66	5.64	2.62	32.63	34.05	1.72	100.74
1.00	9.56	6.24	5.44	3.42	38.25	37.05	0.70	100.66
1.25	5.13	5.43	3.92	4.42	42.54	39.12	0.00	100.56
1.50	3.33	5.04	2.02	6.45	45.35	38.60	0.00	100.79
1.75	1.91	5.13	2.71	6.13	43.63	41.02	0.00	100.53
2.00	1.81	4.32	2.92	6.94	45.34	39.21	0.00	100.54
2.25	0.00	2.89	1.20	9.18	46.79	39.71	0.00	99.77
2.50	0.00	3.20	1.50	7.20	48.94	39.23	0.00	100.07

 

Table 4. First order parameters for hydrolysis of dichlorophenyl and difluorophenyl –labelled lufenuron at various pH-conditions

pH	Temperature   (ºC)	dichlorophenyl–labelled		difluorophenyl –labelled
		Half-life (days)	Correlation (r2)	Half-life (days)	Correlation (r2)
1	70	>> 720	-	-	-
5	25	>> 720	-	>> 720	-
	70	>> 720	-	-	-
7	25	>> 720	-	>> 720	-
	50	4066.0	0.9076	1858.4	0.97003
	70	130.5	0.9648	45.7	0.92429
9	25	9062.8	0.7023	15512.1	0.43542
	50	185.2	0.9637	40.8	0.96601
	70	4.0	0.9933	1.9	0.91087
13	25	39.6	0.9783	30.3	0.99486
	50	3.5	0.9855	2.7	0.99662
	70	0.3	0.9738	0.3	0.98673

 

Validity criteria fulfilled:

yes

Conclusions:

In a hydrolysis study performed in accordance with OECD TG 111 and under GLP conditions, the calculated half-lives of both dichlorophenylring–labelled and difluorophenylring–labelled test substance during pseudo-first order reaction kinetics were >> 30 days for pH 5 (at 25 or 50ºC) and 7 (25ºC) conditions. Thus, it was concluded that the test substance is hydrolytically stable under acidic and neutral conditions. The half-lives of dichlorophenylring–labelled test substance at pH 9 were 377.6, 7.71 and 0.17 days at 25, 50 and 70ºC, respectively. The half-lives of difluorophenylring–labelled test substance at pH 9 were 646.3, 1.7 and 0.08 days at 25, 50 and 70ºC, respectively. Considering pH 9 and ≥ 50ºC condition is unlikely to occur under normal environmental conditions, it was concluded that the substance is hydrolytically stable under basic conditions as well.

Executive summary:

The hydrolysis of the substance was studied according to the OECT TG 111 and EPA 161 -1 guideline, and in compliance with GLP criteria. The test material was labelled at U-14C dichlorophenylring or at U-14C difluorophenylring and incubated under sterile conditions in buffer solutions for concentrations of 0.0087 mg/5 mL – 0.0119 mg/5 mL in brown glass test tubes. The standard range of pH (5, 7 and 9) and temperature (25ºC) conditions were applied to both difluorophenylring-labelled and dichlorophenylring-labelled lufenuron. In addition, a few experiments were conducted under more extreme conditions (pH 1 and 13) and temperature (50 and 70ºC), although not every combination were tested. The samples were placed in a temperature-monitored water bath and shaken at 200 rpm. At intervals, samples were removed and neutralised then either analysed directly or stored frozen at -20ºC. The test substance and its degradation products were partitioned with dichloromethane and the amounts in each phase quantified by LSC and HPLC. The degradates were characterised, after derivatisation where necessary, by MS or GC-MS.

For dichlorophenylring-Iabelled test substance, the recovery of radioactivity was, on average, for all samples 98.8 ± 1.9%. For difluorophenylring-Iabelled test substance, the recovery of was, on average, for all samples 98.0 ± 2.1%. The rate of hydrolysis of difluorophenylring-labelled the test substance under normal environmental conditions (pH 5, 7 or 9) and 25ºC, was extremely slow. Virtually no degradation had occurred at any pH after 30 days. As the temperature was increased to 50ºC, the test substance began to hydrolyse at neutral and alkaline pH. Under standard pH and temperature no degradation was observed at pH 5 and 7. Low amounts of M4, M6 and M8 were registered at pH 9, at levels lower than 4%. The maximum number and amounts of metabolites formed under extreme conditions (pH 9 and 70ºC): Dichlorophenylring-labelled test substance was degraded to M4 (max 25.0% AR) and then to M6 (max 60.9% AR), which are both soil metabolites. Difluorophenylring-labelled test substance was degraded to M7 (max 55.5% AR) derivative, which is also a soil photolysis product and then to M8 (max 32.3% AR) derivative. Both the dichlorophenylring and difluorophenylring labelled compounds produced M2 by loss of fluoride and ring closure. No significant degradation occurred at pH 1 even at 70°C.

The calculated half-lives of both dichlorophenylring–labelled and difluorophenylring–labelled test substance during pseudo-first order reaction kinetics were >> 30 days for pH 5 (at 25 or 50ºC) and 7 (25ºC) conditions. Thus, it was concluded that the test substance is hydrolytically stable under acidic and neutral conditions. The half-lives of dichlorophenylring–labelled test substance at pH 9 were 377.6, 7.71 and 0.17 days at 25, 50 and 70ºC, respectively. The half-lives of difluorophenylring–labelled test substance at pH 9 were 646.3, 1.7 and 0.08 days at 25, 50 and 70ºC, respectively. Considering pH 9 and ≥ 50ºC condition is unlikely to occur under normal environmental conditions, it was concluded that the substance is hydrolytically stable under basic condition as well.

Description of key information

Hydrolytic DT50 at pH 7 at 25 °C >> 30 days, hydrolytically stable under acidic, neutral, and basic conditions, OECD TG 111 and EPA 161 -1, Ellgehausen 1992

Additional information

There is one hydrolysis study available, which followed OECD TG 111 and EPA 161-1 guideline and was in compliance with GLP criteria. The test material was labelled at U-14C dichlorophenylring or at U-14C difluorophenylring and incubated under sterile conditions in buffer solutions for concentrations of 0.0087 mg/5 mL – 0.0119 mg/5 mL in brown glass test tubes. The standard range of pH (5, 7 and 9) and temperature (25ºC) conditions were applied to both difluorophenylring-labelled and dichlorophenylring-labelled lufenuron. In addition, a few experiments were conducted under more extreme conditions (pH 1 and 13) and temperature (50 and 70ºC), although not every combination were tested. The samples were placed in a temperature-monitored water bath and shaken at 200 rpm. The calculated half-lives of both dichlorophenylring–labelled and difluorophenylring–labelled test substance during pseudo-first order reaction kinetics were >> 30 days for pH 5 (at 25 or 50ºC) and 7 (25ºC) conditions. Thus, it was concluded that the test substance is hydrolytically stable under acidic and neutral conditions. The half-lives of dichlorophenylring–labelled test substance at pH 9 were 377.6, 7.71 and 0.17 days at 25, 50 and 70ºC, respectively. The half-lives of difluorophenylring–labelled test substance at pH 9 were 646.3, 1.7 and 0.08 days at 25, 50 and 70ºC, respectively. Considering pH 9 and ≥ 50ºC condition is unlikely to occur under normal environmental conditions, it was concluded that the substance is hydrolytically stable under basic condition as well.