Chlorotrifluoroethylene

Adsorption / desorption

Description of key information

In accordance with section 1 of REACH (Regulation (EC) No 1907/2006) Annex XI the adsorption/desorption test (required in section 9.3.1) and further information on adsorption/desorption (required in section 9.3.3) are not proposed by the registrant as Chlorotrifluoroethylene (CTFE) is a volatile gas at ambient conditions with a boiling point in the range of -26.2°C (The Beilstein database. Reference: Miller - 1951 ) to -26.8°C (The Beilstein database. Reference: Henne - 1948) and a vapour pressure of 612 kPa at 25°C (ISCS No. 0685, NIOSH) . CTFE is also characterized by a moderate water solubility of 380 mg/L. 
The value of water solubility of 380 mg/l was experimental determined in a completely sealed system with an atmosphere saturated with CTFE. Although the value of 380 mg/l itself reveals a moderate water solubility, it represents an overestimation of the actual water solubility of CTFEE in the natural system since the experimental conditions did not represent the natural conditions. 
The Henry’s Law constant of CTFE was calculated to be 31.500 Pa m3/mol (HENRYWIN v3.20, EPI Suite v4.0), suggesting that the substance is expected to rapidly volatilise from water to the air.
Moreover, the Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7a: Endpoint Specific Guidance, Appendix R.7.1-4 indicates that substances with a Henry’s Law constant of around 1 hPa m3/mole rapidly volatilize from water. On the basis of the properties of CTFE it is expected that the substance primarily and rapidly partition to the atmosphere.
The EQC Fugacity Ill Model confirms that the whole amount of CTFE released to air remains in this compartment. The model was run assuming emission only to air. In case of an accidental emission, CTFE is only released to air, because CTFE is a volatile gas at ambient conditions with a boiling point ranging from -26.2°C to -26.8°C.

Additional information

Chlorotrifluoroethylene (CTFE) is a volatile gas at ambient conditions wich is expected to primarily and rapidly partition to atmosphere based on a boiling point in the range of -26.2°C (The Beilstein database. Reference: Miller - 1951 ) to -26.8°C (The Beilstein database. Reference: Henne - 1948), a vapour pressure of 612 kPa at 25°C (ISCS No. 0685, NIOSH) and a moderate water solubility of 380 mg/L.The value of water solubility of 380 mg/l was experimentally determined in a completely sealed system with an atmosphere saturated with CTFE. Althoughthe value of 380 mg/l itself reveals a moderate water solubility, it represents an overestimation of the actual water solubility of CTFE in the natural system since the experimental conditions did not represent the natural conditions.

The Henry’s Law constant of CTFE was calculated to be 31.500 Pa m3/mol (HENRYWIN v3.20, EPI Suite v4.0), suggesting that the substance is expected to rapidly volatilise from water to the air.

In fact: the Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7a: Endpoint Specific Guidance, Appendix R.7.1-4 indicates that substances with a Henry’s Law constant of around 1 hPa m3/mole rapidly volatilize from water; on the basis of the properties of CTFE it is expected that the substance primarily and rapidly partition to the atmosphere. In addition the EQC Fugacity III Model (Version 2.02, The Canadian Centre for Environmental Modelling and Chemistry, May 2003)

confirms that all the CTFE released to atmosphere remains in this compartment. The model was run assuming emission only to air. In case of an accidental emission, CTFE is only released to atmosphere, because CTFE is a volatile gas at ambient conditions with a boiling point ranging from -26.2°C to -26.8°C.

Hence, due to the gaseous nature of the substance and its partition to the atmosphere, as well as the consequent difficulty to appropriately test CTFE and provide meaningful results, no experimental data are reported for the adsorption/desorption endpoint. However, in order to evaluate the soil adsorption hazard profile of CTFE despite the fact that it is expected to rapidly partition to the atmosphere compartment, the results of the KOCWIN model ( v.2.0, EPI Suite v 4.0) are attached.

As indicated in the Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7a: Endpoint Specific Guidance, Appendix R.7.1.15 (Adsorption/Desorption), substances with a Koc below 500 -1,000 L/Kg are generally unlikely to adsorb to sediment. The estimated soil adsorption coefficient of CTFE ( Koc = 94.94 L/Kg from MCI and Koc = 27.02 L/Kg from log Kow) indicates that the potential adsorption of CTFE to soil and sediment is expected to be low.