Reaction Products of Dimethyl hydrogen phosphite and Alcohols C14-18, Even, Linear

Endpoint summary

Additional information

Abiotic degradation; Hydrolysis

Testing was not carried out using Method 111 of the OECD Guidelines for Testing of Chemicals (13 April 2004) and Method C.7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008 for the following reasons. The test item as a whole was expected to be essentially insoluble in water. Therefore the test solution concentration required to dissolve all the components (less than half the water solubility) would be impractically low and a sufficiently sensitive analytical method was not available. The test item is a complex mixture, to which the test method is not ideally suited because each component that is unstable is likely to have its own hydrolytic rate. The main functional group within the components of the test item was a phosphite ester and, although phosphite esters will hydrolyse in both acidic and alkaline conditions, the test item components may have a significantly reduced hydrolytic rate due to them being essentially insoluble in water. Furthermore, the test item as a whole was determined to be readily biodegradable and in accordance with REACH Annex VIII, Section 9.2.1, Column 2, it is not necessary to investigate hydrolysis as a function of pH.

Biodegradation

A study was performed to assess the ready biodegradability of the test item in an aerobic aqueous medium. The method was designed to be compatible with OECD Guidelines for Testing of Chemicals (1992) No 301B "Ready Biodegradability; CO2 Evolution Test" referenced as Method C.4 -C of Commission Regulation (EC) No 440/2008 and US EPA Fate, Transport, and Transformation Test Guidelines OCSPP 835.3110 (Paragraph m).

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 18 to 24 °C for 28 days.

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

The test item attained 73 % biodegradation after 28 days and can therefore be considered to be readily biodegradable. The test item failed to meet the 10 -day window validation criterion whereby 60 % biodegradation must be attained within 10 days of the biodegradation exceeding 10 %. However, in accordance with the Revised Introduction to the OECD Guidelines for Testing of Chemicals (2006), if testing on a complex mixture is performed, and it is anticipated that a sequential biodegradation of the individual structures takes place, then the 10 -day window should not be applied to interpret the results of the test.

The toxicity control attained 65 % biodegradation after 14 days and 96 % biodegradation after 28 days thereby confirming that the test item did not exhibit an inhibitory effect on the sewage treatment micro-organisms used in the test. Sodium benzoate attained 75 % biodegradation after 14 days and 89 % biodegradation after 28 days thereby confirming the suitability of the inoculum and test conditions. The test item attained 73 % biodegradation after 28 days and can therefore be considered to be readily biodegradable.

Adsorption / desorption coefficient (Koc)

Determination of the adsorption coefficient was carried out using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.

The test utilised a high performance liquid chromatograph. A commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties was used. The adsorption coefficient of the UVCB test item was determined to be greater than 4.27 x 10E05 with a Log10 Koc > 5.63 (OECD 121 and EU Method C.19).