tris(branched-alkyl) borate

Endpoint summary

Description of key information

Hydrolysis

The study does not need to be conducted because the substance is readily biodegradable.

Biodegradation

In the key study, the test item attained 74% biodegradation after 28 days. As the test material is a UVCB the 10 -day window validation criterion is not applicable. Therefore, the test material can be considered to be readily biodegradable. The organic degradation product derived from hydrolysis of the test item is readily biodegradable (OECD 301 B and EU Method C.4-C). In a supporting study, conducted in accordance with relevant Chinese guidelines, BOD results showed that biodegradation of the test substance was 63.0 % after 28 days. Based on residue analysis, biodegradation of the test substance was 71.3 % during the test period.

Adsorption coefficient

Adsorption coefficient could not be determined using a procedure designed to be compatible with either OECD Guideline No. 121 or EC Method C19 because the substance is highly unstable in water and hydrolyses rapidly. These hydrolysis products are already registered with partition coefficients available so it was considered that further testing with respect to these components was not required. For boric acid the typical Kp for soil is given as 2.19 L/kg (log Kp=0.34 L/kg) For 2-propyl heptan-1-ol Koc is given as 562.3 (Log Koc = 2.75) The substance is predicted to be mobile in soil.

Additional information

Hydrolysis

Investigation of hydrolysis is technically not possible because the substance has been demonstrated to be hydrolytically unstable in water.

Biodegradation

In the key study performed to OECD Guideline No. 301B and EC Method C.4-C : CO2 Evolution test the test item, at a concentration of 10 mg Carbon/L, was exposed to activated sewage sludge micro-organisms with mineral medium in sealed culture vessels in the dark at approximately 21°C for 28 days.

 

Following the recommendations of ISO 1995, the test item was dissolved in an auxillary solvent prior to being absorbed onto filter paper and subsequent dispersal in the test media. Using this method the test item is evenly distributed throughout the test medium and the surface area of test item exposed to the test organisms is increased thereby increasing the potential for biodegradation.

 

The biodegradation of the test item was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the reference item sodium benzoate, together with a toxicity control were used for validation purposes.

 

The test item is an unstable UVCB substance in aqueous conditions and hydroyses rapidly (less than 30 minutes). The water solubility of the test item is therefore equivalent to the water solubility of the two main degradation products boric acid and 2-propyl heptan-1-ol. Both degradation products have been registered under REACH. Boric acid is an inorganic substance with high water solubility and will not undergo biodegradation. 2-propyl heptan-1-ol is a poorly soluble substance (> 100 mg/L) and is readily biodegradable with over 90% degradation in 28-days.

The test item attained 74% biodegradation after 28 days. As the test material is a UVCB the 10 -day window validation criterion are not applicable. Therefore, the test material can be considered to be readily biodegradable. The organic degradation product derived from hydrolysis of the test item is readily biodegradable.

 

In a supporting study, ready biodegradation of the test item was investigated according to HJ/T 153-2004 “The guidelines for the testing of chemicals, Degradation and Accumulation” (2nd edition) (Beijing: China Environment Press, 2013) and procedure 301 C of the Guidelines for Testing of Chemicals “Modified MITI Test (I) (OECD 1992).

 

Test solutions were prepared in an inorganic salts medium inoculated with a number of microorganisms collected from ten places in Nanjing city. Test substance and microorganisms not adapted to the test item were added to aerobic aqueous medium in BOD bottles. The Biological Oxygen Demand (BOD) and residual chemicals in the BOD bottles were measured over a 28-day period.

 

During the test, the temperature was kept at 24.7 to 25.2 °C and pH was kept at 6.83 to 7.40. Total oxygen uptake in the inoculum blank was 33.4 mg O2/L at the end of the test. Biodegradation of the reference substance (sodium benzoate) reached 71.8 % at 7 days and 75.5 % at 14 days. The difference between replicate values for inoculum blank and test item were both less than 20 %. Biodegradation of the inhibition control was 72.2 % at 14 days indicating there was no inhibitory effect on the inoculum. Oxygen consumption by the test substance was greater than 60 % of inoculum blank. The test was considered valid.

 

The BOD results showed that biodegradation of the test substance was 63.0 % after 28 days. Based on residue analysis, biodegradation of the test substance was 71.3 % during the test period.

 

Adsorption coefficient

The test item could not be determined using a procedure designed to be compatible with either OECD Guideline No. 121 or EC Method C19. The test item is highly unstable in water and hydrolyses rapidly. The guidelines for the HPLC method state that the method is not applicable if the test item reacts with the mobile phase. The test item reacts with water and could potentially react with methanol as it is a protiotic solvent. To assess the assumptions, test injections were performed. The assessment was carried out twice on separate days to confirm the observations. The parameters included: Use of a commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties Mobile phase of methanol:water (55:45 v/v) Gradient over 5 minutes starting at 30 minutes to 100% tetrahydrofuran Primary detection by evaporative light scattering detector and additional check with a variable wavelength detector (210 nm). The test item was nominally prepared at 1000 and 10000 mg/L in tetrahydrofuran (dried over anhydrous sodium sulphate) No definitive peak(s) that represented the test item could be detected. The chromatography of the solvent blank and the test concentrations were essentially the same. The method could not be performed as the test item is decomposing before it could be analysed. Due to the ready hydrolysis of the test item, it would be expected to exist in the environment as its hydrolysis products; boric acid and 2-propyl heptan-1-ol. These components are already registered with partition coefficients available so it was considered that further testing with respect to these components was not required. For boric acid the typical Kp for soil is given as 2.19 L/kg (log Kp=0.34 L/kg) For 2-propyl heptan-1-ol Koc is given as 562.3 (Log Koc = 2.75) The substance is predicted to be mobile in soil.