Silicic acid, ethyl ester

Endpoint summary

Description of key information

Hydrolysis

On the basis of the experimental studies of the structurally and functionally similar read across chemical and applying the weight of evidence approach, the hydrolysis half-life value of the test chemical can be expected to be 4.4 hrs at a temperature range of 25°C and pH 7.0, respectively. Thus, based on this half-life value, it can be concluded that the test chemical can be considered to be moderately hydrolysable in water.

Biodegradation in water

Estimation Programs Interface Suite (2018) was run to predict the biodegradation potential of the test chemical in the presence of mixed populations of environmental microorganisms. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that test chemical is expected to be not readily biodegradable.

Adsorption / desorption

The adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals (Experimental study report, 2018). The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately pipetting 4 microlitre of test item and diluted with Acetonitrile up to 10 ml. Thus, the test solution concentration was 384 mg/l(calculated according to its density). The pH of test substance was 7.8. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to estimated Koc range of the test substance and generalized calibration graph was prepared. The reference substances were Acetanilide, 4-chloroaniline, 4-methylaniline(p-Tolouidine), N-methylaniline, p-toluamide, Aniline, 2,5 -Dichloroaniline, 4-nitrophenol, 2 - nitrophenol, 2-nitrobenzamide, 3-nitrobenzamide, Nitrobenzene, 4 - Nitrobenzamide, 1-naphthylamine, 1-naphthol, Direct Red 81, Benzoic acid methylester, Carbendazim, Benzoic acid phenylester, Xylene, Ethylbenzene, Toluene, Naphthalene, 1,2,3-trichlorobenzene, Pentachlorophenol, Phenol, N,N-dimethylbenzamide, 3,5-dinitrobenzamide, N-methylbenzamide, Benzamide, phenanthrene, DDT having Koc value ranging from 1.25 to 5.3. The Log Koc value of test chemical was determined to be 2.279 ± 0.001 dimensionless at 25°C.This log Koc value indicates that the substance has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

Additional information

Hydrolysis

Data available for the structurally and functionally similar read across chemicals has been reviewed to determine the half-life of the test chemical. The studies are as mentioned below:

 

The half-life of the test chemical was determined. The study was performed according to OECD Guideline 111 (Hydrolysis as a Function of pH). The study was performed at temp. 10, 25 and 35°C and pH 4, 7 and 9, respectively. Test chemical hydrolysis was followed by measuring its disappearance as a function of time by an extraction method using gas chromatography with flame ionization detection (GC-FID). The half-life of test chemical at 25 °C was observed to be 0.11, 4.4, and 0.22 hrs at pH 4, 7, and 9, respectively. At 10 °C, the half-life of test chemical was observed to be 0.20 and 0.76 hrs at pH 4 and 9, respectively. At 35°C, the half-life of test chemical was observed to be 0.073 and 0.12 hrs at pH 4 and 9, respectively. Thus, based on the half-life value (4.4 hrs) at temp. 25 °C and pH 7.0, test chemical is considered to be moderately hydrolysable in water.

 

In an another study, the half-life of the test chemical was determined. Although half-life value of test chemical was not known, but test chemical was reported to be hydrolysable in water after a period of 2 days.

 

On the basis of the experimental studies of the structurally and functionally similar read across chemical and applying the weight of evidence approach, the hydrolysis half-life value of the test chemical can be expected to be 4.4 hrs at a temperature range of 25°C and pH 7.0, respectively. Thus, based on this half-life value, it can be concluded that the test chemical can be considered to be moderately hydrolysable in water.

Biodegradation in water

Predicted data for the test chemical and supporting study for its read across substance were reviewed for the biodegradation end point which are summarized as below:

 

In a prediction using the Estimation Programs Interface Suite (2018), the biodegradation potential of the test chemicalin the presence of mixed populations of environmental microorganisms was estimated. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that test chemical is expected to be not readily biodegradable.

 

For the test chemical, biodegradation study was conducted for 29 days for evaluating the percentage biodegradability of test chemical (Secondary source, 2008). The study was performed according to EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test). Initial test substance conc. used in the study was 39.1 mg/l. Activated sludge, domestic was used as a test inoculum. Inoculum was a living slime from a primary communal sewage treatment plant (Marl-East). Mineral medium and inoculum were placed into the test containers and the test chemical or positive control was introduced. The test containers were sealed and incubated at 20.8 - 22.1 deg C and shaken at approximately 180 rpm. An hour before analysis, sodium hydroxide is added, respectively, to each bottle. The sodium hydroxide is sufficient to absorb the CO2 that is evolved when the test chemical is completely degraded. The degree of biodegradation was recorded on day 0, 1, 4, 8, 13, 18, 21, 26, 28 and 29. The control substance achieved a breakdown rate of 76% within 10 days after an initial exceedance of the 10% breakdown threshold. The percentage degradation of test chemical was determined to be 47% by CO2 evolution parameter in 28 days. Thus, based on percentage degradation, test chemical is considered to be not readily biodegradable in nature.

 

On the basis of above results for test chemical, it can be concluded that the test chemical can be expected to be not readily biodegradable in nature.

Adsorption / desorption

The adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals (Experimental study report, 2018). The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately pipetting 4 microlitre of test item and diluted with Acetonitrile up to 10 ml. Thus, the test solution concentration was 384 mg/l(calculated according to its density). The pH of test substance was 7.8. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to estimated Koc range of the test substance and generalized calibration graph was prepared. The reference substances were Acetanilide, 4-chloroaniline, 4-methylaniline(p-Tolouidine), N-methylaniline, p-toluamide, Aniline, 2,5 -Dichloroaniline, 4-nitrophenol, 2 - nitrophenol, 2-nitrobenzamide, 3-nitrobenzamide, Nitrobenzene, 4 - Nitrobenzamide, 1-naphthylamine, 1-naphthol, Direct Red 81, Benzoic acid methylester, Carbendazim, Benzoic acid phenylester, Xylene, Ethylbenzene, Toluene, Naphthalene, 1,2,3-trichlorobenzene, Pentachlorophenol, Phenol, N,N-dimethylbenzamide, 3,5-dinitrobenzamide, N-methylbenzamide, Benzamide, phenanthrene, DDT having Koc value ranging from 1.25 to 5.3. The Log Koc value of test chemical was determined to be 2.279 ± 0.001 dimensionless at 25°C.This log Koc value indicates that the substance has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.