Sodium long chain alkyl salicylate

Hydrolysis

Description of key information

Not technically possible to determine hydrolysis as a function of pH; OECD 111, EU Method C.7 and EPA OPPTS 835.2120

Additional information

The hydrolysis as a function of pH of the test material was investigated in accordance with the standardised guidelines OECD 111, EU Method C.7 and EPA OPPTS 835.2120 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the principles for assessing data quality set forth by Klimisch et al. (1997).

The rate of hydrolysis of the test material as a function of pH was investigated at buffer solutions at pH values normally found in the environment (pH 4, 7 and 9).

The buffer solutions were filter-sterilised and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. The test material was spiked to the solutions at a target concentration of 2.90 mg/L using a spiking solution in methanol. For each sampling time (5 and 12 days), duplicate sterile PET vessels under vacuum were filled with 6 mL test solution and placed in the dark in a temperature controlled environment at 50.1 ± 0.2 °C.

After 5 days, a relative concentration decrease of 99, 33 and 4.7 % was observed at pH 4, pH 7, and pH 9, respectively. No hydrolysis was expected based on the molecular structure of the test material, therefore, to test whether this concentration decrease is caused by adsorption of test material on the wall of the test tube, additional samples were taken at t = 12 days. From duplicate vessels, one subsample was diluted and the remaining volume was transferred into a glass vial and the vessels walls were flushed with an equal amount methanol.

This experiment indicates that the test material adsorbs to the container wall since the test material concentration analysed after flushing with methanol is higher than the concentration analysed in the subsample. This, along with the low test material concentrations used as a result of the low water solubility of the test material, results in the definitive test for hydrolysis not being technically possible.

Under the conditions of this study, hydrolysis as a function of pH cannot be determined.

In accordance with section 2 of Annex XI of Regulation (EC) No 1907/2006, it is considered justified to omit the full hydrolysis as a function of pH study (required in section 9.2.2.1 of Annex VIII) on the grounds that testing is not technically feasible.

An attempt was made to determine the hydrolysis as a function of pH in a screening study; however, no value could be determined. The test material concentrations employed during the hydrolysis test were very low, since the guideline requires that initial solution concentrations are less than half the water solubility (water solubility 0.00589 g/L) and that the test material is analytically measureable at 10 % of the initial test concentration (i.e. the LOQ is 0.01 mg/L).

A large test material decrease was observed during the preliminary test. Experiments have indicated that adsorbance to container walls causes significant test material loss at these low concentration levels. Together, these factors result in the definitive test for hydrolysis not being technically possible.