ethametsulfuron-methyl (ISO); methyl 2-[(4-ethoxy-6-methylamino-1,3,5-triazin-2-yl)carbamoylsulfamoyl]benzoate

Phototransformation in water

Administrative data

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Study type:

direct photolysis

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 316 (Phototransformation of Chemicals in Water - Direct Photolysis)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: US EPA OPPTS 835.2240

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Reference substance 002

Cas Number:

97780-06-8

Test material form:

solid

Details on test material:

Purity: 98.9%

Study design

Radiolabelling:

yes

Remarks:

[Phenyl(U) label-14C] and [Triazine(U) label-14C]

Analytical method:

high-performance liquid chromatography

Buffers:

pH 7 buffer solution

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

> 280

Duration of test at given test condition

Duration:

21 d

Temp.:

25 °C

Initial conc. measured:

0.28 other: µg/mL

Reference substance:

yes

Remarks:

Unlabeled test substance

Dark controls:

yes

Results and discussion

Transformation products:

no

Remarks:

No degradation products were found above 5% of the total peak area in either the dark, or irradiated samples.

Details on results:

The mean recoveries of the dark control samples over 9 post 0-time sampling intervals (days 1-21) ranged from 99.3% to 101.0% AR. The overall mean recovery in the dark samples was 99.9% AR.

The mean recovery of radioactivity of the irradiated samples over 9 post 0-time sampling intervals (days 1-21) ranged from 100.4% to 110.4% AR. The overall mean recovery in the irradiated samples was 103.9%.

No degradation products were found above 5% of the total peak area in either the dark, or irradiated samples.

Applicant's summary and conclusion

Conclusions:

The test substance is photolytically stable in sterile pH 7 buffer when exposed to continuous artificial light. There were no significant degradation products (i.e., >5% of the total applied radioactivity) determined in the dark or irradiated samples in the study.

Executive summary:

The rate and nature of degradation of radiolabelled test substance after exposure to simulated sunlight for up to 21 days were determined in sterile pH 7 buffer. This was equivalent to ca 30 days of mid-summer sunlight at latitude of N 40°, assuming a 12 h light/12 h dark cycle. The test was conducted at a nominal concentration of 0.28 µg/mL and samples were exposed to continuous irradiation using a xenon arc lamp until removal for analysis at the appropriate time points (after 0, 1, 2, 3, 6, 8, 10, 13, 16, and 21 days). The study was conducted in compliance with OECD Guideline 316 and US EPA OPPTS 835.2240.

Test vessels were prepared for triazine and phenyl labelled test substance. Half of the test vessels containing test material at the fortification level were subjected to light irradiation at each of the 10 sampling periods, including the zero time analysis. The other half of the test vessels were maintained in the dark. Irradiated and non-irradiated (dark control) test vessels were sampled in duplicate (one for each label) after 0, 1, 2, 3, 6, 8, 10, 13, 16, and 21 days and assayed by LSC for radioactivity. Then, each sample was analyzed with comparisons to radiolabelled standards by HPLC–RAM Detector analysis to validate the identity of the test substance chromatographic peak and certain degradates.

The recovery of radioactivity was calculated based on the percentage of the application rate. The mean recoveries of the dark control samples over 9 post 0-time sampling intervals ranged from 99.3% to 101.0% AR. The overall mean recovery in the dark samples was 99.9% AR. The mean recovery of radioactivity of the irradiated samples over 9 post 0-time sampling intervals ranged from 100.4% to 110.4% AR. The overall mean recovery in the irradiated samples was 103.9%.

The concentrations of the test substance in the pH 7 buffer showed no significant decrease in dark or irradiated samples based on percent of total radioactivity during the course of the study. The percentage of the parent compound was above 95% AR in the dark samples during the course of the study. The same results were also obtained in the irradiated samples. The percentage of the parent compound was also above 95% in the irradiated samples, excepting the results of day 13, where the percentage of the parent compound was approximately 90% AR. No degradation products were found above 5% of the total peak area in either the dark, or irradiated samples.

This study demonstrated that the test substance is photolytically stable in sterile pH 7 buffer when exposed to continuous artificial light. There were no significant degradation products (i.e., >5% of the total applied radioactivity) determined in the dark or irradiated samples in the study.