Mecoprop

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

06 June 1986 to 27 August 1986

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-1 (Hydrolysis)

Deviations:

no

GLP compliance:

yes

Remarks:

The work conducted after 16 October 1989, was conducted in accordance with the EPA GLP Standards.

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

Definitive Study
The hydrolysis samples were analysed using procedures outlined. Sampling times were posted on a master calendar and were based on the results of the preliminary investigation, as well as previous analyses. After analysis, the hydrolysis samples were stored in a freezer.

Buffers:

Solvent System A: Chloroform: hexane: glacial acetic acid (80:20:10)
Solvent System B: Toluene: methanol: glacial acetic acid (90:16:8)
Solvent System C: Acetonitrile: water: ammonium hydroxide (80:18:2)
pH 5 Buffer: 0.01 M sodium acetate adjusted to pH 4.99 and pH 5.00 with acetic acid for preliminary and definitive studies, respectively.
pH 7 Buffer: 0.01 M potassium phosphate adjusted to pH 7.00 and pH 7.00 with acetic acid for preliminary and definitive studies, respectively.
pH 9 Buffer: 0.01 M sodium borate adjusted to pH 9.00 and pH 9.01 with sodium hydroxide and/or acetic acid for preliminary and definitive studies, respectively.

Details on test conditions:

Preliminary Investigation
Sample Preparation and Fortification: Aliquots (3.5 mL) of each aqueous buffer solution were placed in separate glass vials (three) and Spectro-cells (six). These were capped and autoclaved for 4 hours at 122 °C. To minimise the headspace, an additional 0.5 mL of each buffer solution was added for a total of 4.0 mL. To three of the Spectro-cells, 40 µL of acetone was added as a sensitiser. The glass vials were wrapped with aluminium foil. The fortification solution was prepared by mixing 14C-test material and analytical-grade test material in acetonitrile (ACN). Each vial and cell were fortified with 30 µL of the test material solution to obtain a final concentration of 41 ppm [1.2 µCi 14C-test material as determined by liquid scintillation counting (LSC)]. The cells and vials were placed in an inverted position between four Chroma 50 artificial lamps (two on each side) and maintained at approximately 25 °C.

Definitive Study
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: Glass vials and Spectro-cells. All vials and cells were labelled with a unique sample number, the study number, and a description of the matrix. For each of the three pH groups there were two sets of glass vials (five vials each) and two sets of Spectro-cells (five cells each).
- Sterilisation method: The cells and vials were sterilised by autoclaving for 4.25 hours at 122 °C.
- Measures taken to avoid photolytic effects: All glass vials were wrapped in aluminium foil to prevent light exposure.

TEST MEDIUM
- Preparation of test medium: Aliquots (4.0 mL) of each aqueous buffer solution were placed in separate cells and vials and capped. To one set of Spectro-cells at each pH, 40 µL of acetone was added as a sensitiser. The fortification solution was prepared by mixing 14C-test material and analytical-grade test material in ACN. Each vial and cell were fortified with 40 µL of the test material solution. Pre-, mid-, and post-fortification aliquots were removed from the test material solution to determine the amount of test material applied. The final concentrations in the cells and vials were 52 ppm (4.4 µCi) for the hydrolysis samples.

OTHER TEST CONDITIONS
- The hydrolysis vials were placed in the dark and maintained at 25 °C ± 2° C. Temperature was recorded using a Dickson Minicorder.

pH:

5

Temp.:

25 °C

Initial conc. measured:

52 other: ppm

pH:

7

Temp.:

25 °C

Initial conc. measured:

52 other: ppm

pH:

9

Temp.:

25 °C

Initial conc. measured:

52 other: ppm

Number of replicates:

Five

Positive controls:

no

Transformation products:

not specified

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

The test material was hydrolytically stable for the study period.

pH:

5

Temp.:

25 °C

Remarks on result:

other: Hydrolytically stable for the study period.

pH:

7

Temp.:

25 °C

Remarks on result:

other: Hydrolytically stable for the study period.

pH:

9

Temp.:

25 °C

Remarks on result:

other: Hydrolytically stable for the study period.

Percent Recovery and Percent Test Material Remaining in Aqueous pH 5 Buffer Samples

Matrix	Duration (Hours)	Recovery (%)	TLC Fraction of Test Material (%)	Test Material Remaining (%)
Hydrolysis	5.4	105	96.91	102
	107	106	97.61	103
	194	106	92.57	98.1
	345	107	97.47	104
	751	108	9.27	103

 

Percent Recovery and Percent Test Material Remaining in Aqueous pH 9 Buffer Samples

Matrix	Duration (Hours)	Recovery (%)	TLC Fraction of Test Material (%)	Test Material Remaining (%)
Hydrolysis	1.4	50.6*	96.96	N/C
	65.8	111	97.25	108
	190	115	96.60	111
	321	107	97.46	104
	740	112	97.96	110

*: Low recoveries attributed to inadequate mixing.  Values were not used in subsequent calculations.

N/C: No calculations performed.

 

Duration and Final pH Values for Aqueous pH 5 Buffer Samples

Matrix	Duration (Hours)	Final pH
Hydrolysis	5.4	5.02
	107	4.98
	194	4.02
	345	5.00
	751	4.97

Initial pH was determined to be 5.00

 

Duration and Final pH Values for Aqueous pH 7 Buffer Samples

Matrix	Duration (Hours)	Final pH
Hydrolysis	5.3	6.99
	107	6.97
	194	6.95
	345	6.94
	751	7.00

Initial pH was determined to be 7.00

 

Duration and Final pH Values for Aqueous pH 9 Buffer Samples

Matrix	Duration (Hours)	Final pH
Hydrolysis	1.4	8.96
	65.8	8.96
	190	8.97
	321	8.98
	740	8.93

Initial pH was determined to be 9.01

 

First Order Treatment of Percentage Test Material Remaining

Sample Description	Y-intercept	Slope	Coefficient of Correlation	Calculated Half Life (Hours)
pH 5 hydrolysis	2.01	7.01E-06	0.18622	N/C
pH 7 hydrolysis	2.03	-3.59E-06	-0.68915	N/C
pH 9 hydrolysis	2.03	5.4E-06	0.12389	N/C

N/C: Half-life not calculated.

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of the study, the test material was hydrolytically stable for the study period.

Executive summary:

The hydrolysis of the test material was assessed according to EPA Guideline N 161-1 and in compliance with GLP.

Hydrolysis vials containing the test material at 52 ppm at pH 5, pH 7 and pH 9 were placed in the dark and maintained at 25 °C ± 2° C. Temperature was recorded using a Dickson Minicorder.

Under the conditions of the study, the test material was hydrolytically stable for the study period.

Description of key information

Key Study: Obrist (1986)

Under the conditions of the study, the test material was hydrolytically stable for the study period.

Additional information

Key Study: Obrist (1986)

The hydrolysis of the test material was assessed according to EPA Guideline N 161-1 and in compliance with GLP. The study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

Hydrolysis vials containing the test material at 52 ppm at pH 5, pH 7 and pH 9 were placed in the dark and maintained at 25 °C ± 2 °C. Temperature was recorded using a Dickson Minicorder.

Under the conditions of the study, the test material was hydrolytically stable for the study period.