Reaction mass of chlorodifluoroacetic acid and trifluoroacetic acid

Adsorption / desorption

Description of key information

Based on the available experimental data on each constituent, the reaction mass is considered to have a low potential of adsorption.

Key value for chemical safety assessment

Koc at 20 °C:

30.2

Additional information

No data is available on the reaction mass of chlorodifluoroacetic acid and trifluoroacetic acid. Reliable data are available on the constituents of the reaction mass as described below:

High Performance Liquid Chromatography (HPLC) was used to estimate the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge of CDFA according to the OECD Testing Guideline 121. Only 5 reference substances were used for the calibration curve instead of 6, but as there was at least one below and one above the retention time of the test item, this deviation is not considered to have impacted the quality of the study.

The results showed a Koc value of 30.2, and a log Koc of 1.48. Therefore, the test substance CDFA has a low potential of adsorption on soil and on sewage sludge.

 

The adsorption potential of TFA on soil was studied on the sodium salt of this acid (i.e. sodium trifluoroacetate, CAS RN 2923-16-2). The read-across approach is relevant for the assessment of the Koc because in the environment, this acid is neutralised by cations in presence, including Na+. Additionally, Trifluoroacetic acid and sodium trifluoroacetate are both very soluble in water. This screening test was carried out according to OECD guideline 106 with three soil types. A stock solution of 1000 mg/L NaTFA in water was prepared by mixing about 10 mg NaTFA with 10 mL water. The soil/water-system consisted of about 2 g soil and about 10 mL 0.01 M Ca(CH3COO)2 solution spiked with NaTFA (sodium trifluoroacetate) on a level of about 5 mg/L. Six blanks (without NaTFA), three controls (without soil) and six test soil (two replicates per soil) were performed during the test. Gentle agitation started immediately after the soil was added to the test solution. Agitation was continued for 16 hours (20°C) and sufficient to maintain the soil in suspension. After agitation, the suspension was centrifuged for 10 minutes to obtain a clear solution. The aqueous phase was stored under refrigeration to minimize biodegradation and was analysed for parent compound concentration. The controls and the aqueous phases of the blanks and test systems were analysed for NaTFA concentration by means of ion chromatography, placed in the anion mode.

The conclusion drawn from this study is that the TFA-anion poorly adsorbs to the different soil components because after 16 hours of agitating in a soil/water system less than 3% of the initial amount of TFA had disappeared from the water phase. Due to the fact that less than 25% is adsorbed, no further testing was required by the OECD guidelines.

 

Consequently, considering that both constituents of the reaction mass have a low potential of adsorption on soil and on sewage sludge, the reaction mass of chlorodifluoroacetic acid and trifluoroacetic acid has a low potential of adsorption on soil and on sewage sludge.