N-(2-ethylhexyl)-8,9,10-trinorborn-5-ene-2,3-dicarboximide

Phototransformation in water

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

05 Aug 1991 to 30 Jan 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-2 (Photodegradation Studies in Water)

Version / remarks:

June 25, 1991

Deviations:

not specified

GLP compliance:

yes

Specific details on test material used for the study:

The 14C-MGK 264 (Figure 1) was received from Amersham Corporation, Arlington Heights, Illinois, on October 2, 1990.

The batch number was JB3163.

The radiolabeled 14C-MGK 264 was supplied in fifteen ampules, labeled A-O, each containing 0.5 mCi of 14C-MGK 264.

The stated specific activity was 18.4 mCi/mmol (148,000 dpm/ug). The material was a clear liquid.

Stock solution was purified to 98.5% by HPLC.

Radiolabelling:

yes

Remarks:

14C

Analytical method:

high-performance liquid chromatography

Details on sampling:

Analysis of Test Samples
Exposed and dark control samples were analyzed by the following method on days 0, 1, 3, 7, 14, 21, and 30:

1. Triplicate 100-ul aliquots of each sample were analyzed by LSC for 14C-activity.

2. The pH of each sample was measured using a Coming Model 140 pH meter.

3. Each sample was characterized by using the previously described HPLC method. The injection volume of each sample was 100-uI.

Buffers:

A 0.1-M stock of pH 7 (Tris) buffer was prepared by combining 250 mL of 0.2 M HCI (16.7 mL of 12 M HCI to 1000 mL water) with 235 mL of 0.2 M Tris (hydroxymethyl) aminomethane (24.2 g of Tris in 1000 mL water). The solution was diluted to 1000 mL with water and adjusted to pH 7 with 1.0N KOH.

A 0.01-M pH 7 (Tris) buffer was prepared by combining 50 mL of 0.1-M pH 7 (Tris) stock with 450 mL of Milli-Q water. The pH was readjusted to 7 using 1.0 N KOH and 0.2 M HCI. All glassware used was previously sterilized by autoclaving for at least 30 minutes at 2500 P
(121°C) and 15 psi.

Light source:

Xenon lamp

Remarks:

The light source employed was an Atlas 6500 watt xenon arc lamp. Borosilicate inner and outer filters encase the burner tube to remove UV output below 290 nm.

Light spectrum: wavelength in nm:

> 290

Relative light intensity:

ca. 0.5

Details on light source:

Xenon Light Source
The light source employed was an Atlas 6500 watt xenon arc lamp. Borosilicate inner and outer filters encase the burner tube to remove UV output below 290 nm. The spectral irradiance of the lamp was measured with a LI -COR LI -1800· spectral radiometer before and after the exposure period. The test samples were continuously exposed; therefore, the samples were placed so the light reaching them was one-half the intensity of sunlight (Figure 3, Tables I and II).

Details on test conditions:

Twenty-four borosilicate glass culture tubes were completely filled to ensure zero head space and were sealed with Teflon lined screw caps. Two samples were set aside: one designated as the day 0 sample, the other sample to serve as a source for microbial analysis to check sterility. Twelve of the remaining samples were wrapped in aluminium foil and place in a closed box in the photolysis chamber to serve as non-exposed control samples. The remaining twelve samples were placed in the photolysis chamber and exposed to the xenon arc lamp. (See Figure 3.) The photolysis chamber was maintained at a temperature of 25.6 ± 0.7 °C.

Duration:

30 d

Temp.:

25 °C

Initial conc. measured:

1 other: ug/mL (nominal)

Reference substance:

no

Dark controls:

yes

Computational methods:

The concentration of 14C-MGK 264 in the test sample was determined by multiplying the total 14C-activity found in the sample, expressed as 14C MGK 264 equivalents in ug/mL, by the fraction that was determined to be 14C-MGK 264 by HPLC. The concentrations found at each time point were divided by the values found at time 0 to give a percent of time 0.

The degradation rate of 14C-MGK 264 was calculated assuming first-order kinetics. The natural logarithm of the percent of time 0 concentration was plotted versus time, and linear regression analysis of equation 2 determined the slope of the line. The absolute value of the slope of the line yields k, the rate constant. The half life is then calculated from the rate constant.

Preliminary study:

Preliminary study - duplicate samples at pH 5, 7 and 9 incubated at ca 25°C for 3 days - amount of hydrolysis products recorded in each sample was < 10%.

Parameter:

not specified

Key result

% Degr.:

ca. 4.5

Sampling time:

30 d

Test condition:

pH 7, 25C

Remarks on result:

other: 4.5% degradation seen in both exposed and dark control samples after 30 days

Key result

Test condition:

30 days, pH 7, 25C

Remarks on result:

not determinable

Remarks:

No significant degradation of parent compound was observed during the 30-day study. The rate constants (slope of degradation rate curves) were not significantly different than 0; therefore, half-lives for both exposed and dark control samples were defined as infinite.

Predicted environmental photolytic half-life:

Not applicable - MGK 264 is photolytically stable in an aqueous buffered solution at pH 7 when maintained under sterile conditions at 25.6 ± 0.7 °C.
No significant degradation of parent compound was observed during the 30-day study. The rate constants (slope of degradation rate curves) were not significantly different than 0; therefore, half-lives for both exposed and dark control samples were defined as infinite.

Transformation products:

no

Details on results:

No significant degradation of parent compound was observed during the 30-day study. The rate constants (slope of degradation rate curves) were not significantly different than 0; therefore, half-lives for both exposed and dark control samples were defined as infinite.

No significant degradation of parent compound was observed during the 30-day study. The rate

constants (slope of degradation rate curves) were not significantly different than 0; therefore,

half-lives for both exposed and dark control samples were defined as infinite.

Confirmation of the percent of MGK 264 in the 30-day samples was determined by TLC. The

TLC confirmational results are presented in Table IX. The percent dpm recovered as 14C-MGK

264 was 89.9% and 90.1 % for the exposed and dark control samples, respectively. Additional

analysis by mass spectrometry was performed on the day-30 exposed sample. The results of the

mass spectrometry analysis confirmed that MGK 264 remained stable (Figures 11-14).

The pH of all samples was measured and is shown in Table III. No significant changes were

observed in any of the sample pH measurements (standard deviation of ±0.03 and ±0.04 for

the exposed and dark control test samples, respectively).

The sterility of the test samples was verified by conducting total plate count analysis for bacterial

and fungal populations on the day-O and day-30 samples.

The total 14C-activity in the samples (µg/mL as parent equivalents) was used to determine the

14C-mass balance. The mean mass balance was 95.5% and 95.5% for the exposed and dark

control test samples, respectively (Table III).

Validity criteria fulfilled:

yes

Conclusions:

No significant degradation of parent compound was observed during the 30-day study. The rate
constants (slope of degradation rate curves) were not significantly different than 0; therefore,
half-lives for both exposed and dark control samples were defined as infinite.

MGK 264 is photolytically stable in an aqueous buffered solution at pH 7 when maintained under
sterile conditions at 25.6 ± 0.7 °C.

According to the current guidance (OECD guideline 316): If the estimated half-life (assuming a maximum direct photolysis rate constant) is>30 d, direct photolysis is considered to be an insignificant process. Since the calculated half-life is calculated to be not statistically different from infinite direct photolysis can therefore be considered to be an insignificant process in the environmental breakdown of MGK 264.

Executive summary:

A photolysis study was conducted with MGK 264 at a nominal test concentration of 1.0µg/mL in aqueous solution buffered at pH 7 in 10.0 mM Tris (hydroxymethyl) aminomethane. The samples were photolyzed using a xenon arc lamp in a temperature-controlled photolysis chamber. To determine the percent MGK 264 in each test sample, high performance liquid chromatography was used. Liquid scintillation counting was used to determine the total amount of radioactivity present at each sample point.

 

The data generated during this study prove that 14C-MGK 264 in aqueous solution at pH 7, 25°C, and exposed to light for 30 days does not photolyze. Because of the lack of degradation, the rate constant was determined to be statistically not significantly different from 0, yielding an infinite half-life.

 

Thin-layer chromatography was used to confirm the percent MGK 264 in the terminal samples (day 30). Additional analysis by mass spectrometry was performed on the day-30 exposed sample and confirmed that MGK 264 remained stable.

 

The overall 14C-mass balance indicated no significant loss of 14C-activity from any of the test samples. The mean 14C-mass balance for the exposed and dark samples was 95.5% and 95.5%, respectively.

According to the current guidance (OECD guideline 316): If the estimated half-life (assuming a maximum direct photolysis rate constant) is>30 d, direct photolysis is considered to be an insignificant process. Since the calculated half-life is calculated to be not statistically different from infinite direct photolysis can therefore be considered to be an insignificant process in the environmental breakdown of MGK 264.

Description of key information

A photolysis study was conducted with MGK 264 at a nominal test concentration of 1.0 µg/mL in aqueous solution buffered at pH 7 in 10.0 mM Tris (hydroxymethyl) aminomethane. The samples were photolyzed using a xenon arc lamp in a temperature-controlled photolysis chamber. To determine the percent MGK 264 in each test sample, high performance liquid chromatography was used. Liquid scintillation counting was used to determine the total amount of radioactivity present at each sample point.  

The data generated during this study show that [14C]-MGK 264 in aqueous solution at pH 7, 25°C, and exposed to light for 30 days does not photolyze. Due to the lack of degradation, the rate constant was determined to be statistically not significantly different from 0, yielding an infinite half-life.

According to the current guidance (OECD Guideline 316): If the estimated half-life (assuming a maximum direct photolysis rate constant) is>30 d, direct photolysis is considered to be an insignificant process. Since the calculated half-life is calculated to be not statistically different from infinite direct photolysis can therefore be considered to be an insignificant process in the environmental breakdown of MGK 264.

Additional information

Due to the lack of degradation, the rate constant was determined to be statistically not significantly different from 0, yielding an infinite half-life.