Vinyl 2-ethylhexanoate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Deviations:

yes

Remarks:

The following deviation from the study plan occurred: The test vessels were aerated using continuous aeration at the lowest aeration rate stated in the test guidelines of 0.5 L/min rather than intense stirring stated in the Study Plan. This deviation was

GLP compliance:

yes

Specific details on test material used for the study:

Identification: Vinyl 2-ethylhexanoate
CAS Number: 94-04-2
EC Number: 202-297-4
Batch: PM9CEH01
Purity: 99.6%
Physical state / Appearance: Clear colorless liquid
Expiry date: 04 January 2022
Storage conditions: Room temperature in the dark over silica gel

Analytical monitoring:

yes

Test organisms (species):

activated sludge of a predominantly domestic sewage

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

1 h

Details on test conditions:

Test Item Preparation
Activated sewage sludge micro-organisms were exposed to a series of nominal test concentrations of 10, 100 and 1000 mg/L. The test item was dispersed directly in water.
Nominal amounts of test item (5, 50 and 500 mg) were each separately dispersed directly, in duplicate, in five minute intervals per concentration, with a two minute difference between Time 0 and the +1-Hour vessels with synthetic sewage (16 mL) and deionized reverse osmosis water to a final volume of 250 mL, prior to the addition of activated sewage sludge (250 mL) to give a final volume of 500 mL to give the required concentrations of 10, 100 and 1000 mg/L.
The control group was maintained under identical conditions but not exposed to the test item.

Preparation of Test System
At time "0", 16 mL of synthetic sewage was diluted to 250 mL with water and 250 mL of inoculum added in a 500 mL conical flask (first control) which was provided for analytical analysis. Two minutes later the duplicate control vessel was prepared and aerated with clean, oil-free compressed air at a rate of 0.5 L per minute for 1 hour. Thereafter, at 5 minute intervals from the set-up of the first vessel in each group the procedure was repeated for the test item vessels. The first vessel in each group was sacrificed for analytical analysis and the second vessel was aerated for 1 hour prior to being sacrificed for analytical analysis,
The test was conducted under normal laboratory lighting in a temperature controlled room at a measured temperature of approximately 21 °C.

Compound Specific Analyses
Compound specific analyses were carried out on the Time 0 and Time+1-Hour vessels after being subjected to aeration at a rate of 0.5 L/min from the control and test item vessels (see Annex 4). The lowest rate of aeration of 0.5 L/min was employed in order to minimise any potential loss of test item from the preparations. Aeration by magnetic stirring was considered not appropriate to use as previous has indicated that a fast stirring speed would have to be employed in order to maintain the dissolved oxygen concentration above 60% saturation which would have resulted in a significant loss of test item from the test preparations.

Key result

Duration:

1 h

Remarks on result:

not determinable because of methodological limitations

Remarks:

See details

Details on results:

The test item was insoluble in mineral media (see Annex 2) at a concentration of 100 mg/L with the aid of shaking by hand for approximately 1 minute followed by ultrasonication for 30 minutes and then high shear mixing at approximately 7500 rpm for 15 minutes.
After 30 minutes of passing a stream of compressed air over a known amount of the test item, 38% loss of test item was observed, this had increased to a 58% loss after 60 minutes and 64% loss of test item after 70 minutes.
The test item was found to be extremely volatile (see Annex 3).
Analytical analysis confirmed that the test concentrations could not be maintained in the test preparations over an aeration period of 1 hour (see Annex 4). It is unclear why values of 277% and 137% of nominal in the 10 and 100 mg/L test concentrations at 0 hours and then no test item was detected after 1 hours aeration in the 100 mg/L test vessel. Each weighing of the test item was correct and the results from the procedural recoveries indicate that the analytical method was appropriate.

Validity criteria fulfilled:

not applicable

Conclusions:

As the test item concentrations could not be maintained after 1 hours aeration it will not be possible to conduct this study.
The study was therefore cancelled.

Executive summary:

Introduction
The Toxicity to Activated Sludge in a Respiration Inhibition Test study design requires the test vessels to be subjected to aeration using continuous aeration by compressed air or intense stirring to maintain the dissolved oxygen concentration in the vessels above 60% saturation and to maintain the sludge flocs in suspension.
A solubility, volatility and preliminary test with analytical analysis was initially performed which showed that the test item was extremely volatile over a 70 minute period. The study was therefore cancelled.

Preliminary Solubility Work
A nominal amount of test item (100 mg) was dispersed in reverse osmosis water (1 L) with the aid of shaking by hand for approximately 1 minute followed by ultrasonication for 30 minutes and then high shear mixing at approximately 7500 rpm for 15 minutes and formed a hazy dispersion with an oily film of test item visible at the surface.

Preliminary Volatility Check
A known amount of test item (1.0003 g) was weighed onto a watch glass and a steady stream of compressed air passed over the test item at a rate of 0.5 L/minute. The weight of test item remaining on the watch glass was determined every 10 minutes contact time for 70 minutes which showed a 38% and 64% loss of test item after 30 minutes and 70 minutes respectively.

Preliminary Analytical Check
Analytical analysis confirmed that the test concentrations could not be maintained in the test preparations over an aeration period of 1 hour with values of 277, 137 and 94% of nominal at Time 0 for the test concentrations of 10, 100 and 1000 mg/L decreasing to values of 5 and 22% of nominal for the test concentrations of 10 and 1000 mg/L after 1 hour of aeration. No test item was measured after 1 hour in the test concentration of 100 mg/L (see Annex 4).
It is unclear why values of 277% and 137% of nominal in the 10 and 100 mg/L test concentrations at 0 hours and then no test item was detected after 1 hours aeration in the 100 mg/L test vessel. Each weighing of the test item was correct and the results from the procedural recoveries indicate that the analytical method was appropriate.

Description of key information

As the test item concentrations could not be maintained after 1 hours aeration it will not be possible to conduct this study.
The study was therefore cancelled.