Prometryn

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 Jul 1987 to 20 Nov 1987

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)

GLP compliance:

yes

Radiolabelling:

yes

Remarks:

ring labelled

Analytical monitoring:

yes

Details on sampling:

For each sampling period, 1 mL of solution was aseptically removed from each of the 9 flasks. Three 50 µL aliquots were removed for radioassay. The remainder of the . aliquoted solution (0.85 mL) was fortified with 100 µL of an authentic reference standard stock solution containing 0.2 mg/mL of each standard in methanol (final concentration of each standard was 0.021 mg/mL). These fortified samples were then stored in foil-covered vials at 4° C until HPLC analysis. All samples were analyzed within 7 days.

Buffers:

Aqueous buffered solutions were prepared at pH 5, 7 and 9 with the following compositions.
- pH 5 (Acetic acid - Sodium acetate): 146 mL of 0.1 N Acetic Acid was added to 100 mL of 0.1 N NaOH, Distilled water added to a final volume of one liter, giving a solution at pH 4.85, Adjusted to pH 5.00 with 0.1 N NaOH
- pH 7 (Potassium Dihydrogen Phosphate - Disodium Hydrogen Phosphate): 25.8 mL of 0.1 M Disodium Hydrogen Phosphate was added to 22.4 mL of 0.1 M Potassium Dihydrogen Phosphate, distilled water added to a final volume of one liter, giving a solution at pH 6.95, adjusted to pH 7.00 with 0.1 N NaOH
- pH 9 (Sodium Borate - HCl): 46 mL of 0.04 N HCI was added to 500 mL of 0.01 M Sodium Borate, distilled water added to a final volume of one liter, giving a solution at pH 8.85, adjusted to pH 9.00 with 0.1 N NaOH.
After preparation all buffered solutions were autoclaved for use in the hydrolysis study.

Details on test conditions:

PREPARATION OF SAMPLES FOR HPLC ANALYSIS
The fortified test solutions were radioassayed prior to HPLC analysis to provide for accountability calculations upon HPLC analysis. Solutions (250µL) were directly injected onto the HPLC.

Duration:

30 d

Temp.:

25 °C

Initial conc. measured:

1.54 g/L

Remarks:

For pH 5, 7 and 9

Number of replicates:

3

Positive controls:

no

Negative controls:

no

Transformation products:

no

Key result

pH:

5

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

7

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

9

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

hydrolytically stable based on preliminary test

Details on results:

PURITY OF [14C]-SUBSTANCE
The radiochemical purity of [14C]-substance used in this study was determined by HPLC analysis to be 98.49%.

MATERIAL BALANCE OF [14C]-SUBSTANCE THROUGHOUT STUDY PERIOD
The concentration of [14C]-substance equivalents remained very stable throughout the entire study period having a mean + S.D. of 1.71 + 0.13 ppm for all 3 pHs.
The data establish that substance is not degraded to volatile products or CO2 under the test conditions employed in this study.

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC)
The HPLC method developed for use in this study provides for baseline resolution of the substance and its degradates. The recovery of radiocarbon during HPLC analysis of test solutions was also
established for each sample analyzed. The mean recovery was 99.6 ± 13.3% of the injected radiocarbon.

HYDROLYSIS OF [14C]-SUBSTANCE
Quantitative characterization of radiocarbon present in solutions incubated for 30 days at pH 5, 7, 9 revealed no hydrolysis of [14C] -substance under these conditions. With the exception of the day 7 samples, >90% of the radiocarbon in solution was identified as the substance. It is most likely that the observed degradation in the 7 day sample is due to contamination and does not, in fact, represent hydrolytic breakdown of [14C] -substance. The pH of all test solutions was measured at the end of the 30 day incubation period and found to be identical to the initial pH. The substance is therefore not subject to hydrolytic degradation at pH 5, 7 or 9 over a period of 30 days.

Table 1. Concentration of 14C-substance equivalents in Test Solutions Throughout the Study period

Days of incubation	Concentration (ppm)of 14C-substance equivalents At:
	pH 5			pH7			pH9
	A	B	C	A	B	C	A	B	C
0	1.61	1.63	1.59	1.52	1.54	1.61	1.51	1.52	1.56
1	1.58	1.63	1.87	1.72	1.47	1.53	1.56	1.63	- (1)
3	1.62	1.67	1.75	1.67	1.68	1.44	1.90	1.65	1.88
7	1.03	1.67	1.66	1.69	1.69	1.70	1.65	1.66	1.63
10	1.66	1.70	1.66	1.70	1.81	1.76	1.71	1.68	1.67
15	1.80	1.78	1.70	1.79	1.85	1.78	1.89	1.64	1.86
20	1.77	1.73	1.81	1.86	1.77	1.82	1.68	1.73	1.76
25	1.79	1.80	1.78	1.87	1.96	1.83	1.76	1.75	1.70
30	1.77	1.83	1.78	1.87	1.82	1.84	1.81	1.81	1.79

(1) Data not available - sample lost during analysis

Validity criteria fulfilled:

not specified

Conclusions:

No hydrolysis of the parent [14C]-substance was observed under these conditions.

Executive summary:

Aqueous buffered solutions of [14C]-substance (pH 5, 7, and 9) were incubated at 25 ± 1 ° C for 30 days. [14C]-substance was found not to undergo hydrolytic degradation when tested according to FIFRA Pesticide Assessment Guidelines, Subdivision N. Chemistry: Environmental Fate S161-2 and in compliance with GLP under these conditions. 

 

Description of key information

All available data were assessed and the most representative study is included here as key study.

[14C]-substance was found not to undergo hydrolytic degradation under the test conditions, OECD TG 111; Kesterson 1988.

Additional information

Aqueous buffered solutions of [14C]-substance (pH 5, 7, and 9) were incubated at 25 ± 1 ° C for 30 days. [14C]-substance was found not to undergo hydrolytic degradation when tested according to FIFRA Pesticide Assessment Guidelines, Subdivision N. Chemistry: Environmental Fate S161-2 and in compliance with GLP under these conditions.