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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
2018-05-29
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
1. SOFTWARE
EPIWIN v4.1

2. MODEL (incl. version number)
MPBPWIN v1.43

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CN(Cl)(C)(C)CCO

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
please refer to the attached QMRF

5. APPLICABILITY DOMAIN
please refer to the attached QPRF

Qualifier:
according to guideline
Guideline:
other: REACH guidance on QSAR R.6, May 2008
Deviations:
not applicable
Principles of method if other than guideline:
- Software tool(s) used including version:
EPIWIN v4.1
- Model(s) used:
MPBPWIN v1.43
- Model description: see field 'Attached justification'
- Justification of QSAR prediction: see field 'Attached justification'
Specific details on test material used for the study:
CN(Cl)(C)(C)CCO
Temp.:
25 °C
Vapour pressure:
0 Pa
Remarks on result:
other: Modified Grain Method (MPBPWIN v1.43), prediction for pure choline chloride
Temp.:
25 °C
Vapour pressure:
2 287.2 Pa
Remarks on result:
other: calculated for 75% aqueous solution of choline chloride using Raoult´s law and an experimental vapor pressure value for water of 3172.5 Pa at 25°C

The calculation is done by three different methods: Antoine, Modified Grain and Mackay, whereby the Modified Grain method is preferentially utilized.

By taking this method into account the substance has a vapour pressure of 6.57 * E-8 Pa at 25 °C.

 

Table 1: Estimated vapour pressures for pure choline chloride

Parameter

Method

Result

Vapour pressure

Antoine Method (MPBPWIN v1.43)

1.52 * E-8 Pa /

1.14 * E-10 mm Hg

Mackay Method (MPBPWIN v1.43)

1.1 * E-5 Pa /

8.26 * E-8 mm Hg

Modified Grain Method

(MPBPWIN v1.43)– most relevant

6.57 * E-8 Pa /

4.93 * E-10 mm Hg

 

The vapour pressure of the 75% aqueous solution of choline chloride was calculated according Raoult´s law using a vapour pressure of 3172.5 Pa at 25°C via mole fractions. In a 75% aqueous solution of choline chloride, the mole fractions are:

0.2791 (choline chloride)

0.7209 (water)

Hence, the vapour pressure of a 75% aqueous solution of choline chloride at 25°C can be calculated as:

 

VP =6.57 * E-8 Pa *0.2791 + 3172.5 Pa * 0.7209 = 2287.2 Pa

Conclusions:
The vapour pressure of the pure choline chloride was predicted to be 6.57 * E-8 Pa / 4.93 * E-10 mm Hg at 25 °C using the Modified Grain method of MPBPWIN program v1.43. For the calculation an estimated boiling point of 380.89°C was used. As the substance is marketed as an 75% aqueous solution, the vapour pressure was calculated using Raoult´s law and an experimental vapor pressure value for water of 3172.5 Pa at 25°C, resulting in a calculated vapour pressure of 2287.2 Pa at 25°C which is in the scientifically expected range as it is close to the vapour pressure of water.
Executive summary:

The estimation of vapour pressure (as well as melting and boiling point) can be done by the MPBPWIN program (v 1.43) made available by the U.S. Environmental Protection Agency. This program requires just the input of the chemical structure of the desired compound by SMILES notation. The calculation is done by three different methods: Antoine, Modified Grain and Mackay, whereby the Modified Grain method is preferentially utilized. By taking this method into account and using an estimated boiling point of 380.89°C, pure choline chloride has a vapour pressure of 6.57 * E-8 Pa / 4.93 * E-10 mm Hg at 25 °C. Using Raoult´s law and an experimental vapor pressure value for water of 3172.5 Pa at 25°C, the vapour pressure of a 75 % solution of choline chloride can be calculated to 2287.2 Pa at 25°C. The result was gained by a scientifically accepted calculation method.

Description of key information

Vapour pressure:
6.57 * E-8 Pa / 4.93 * E-10 mm Hg at 25 °C (Modified Grain Method (MPBPWIN v1.43), calculated for pure choline chloride)
2287.2 Pa at 25°C (Modified Grain Method (MPBPWIN v1.43), calculated for 75% aqueous solution of choline chloride via Raoult´s law)

Key value for chemical safety assessment

Vapour pressure:
2 287.2 Pa
at the temperature of:
25 °C

Additional information

The estimation of vapour pressure (as well as melting and boiling point) can be done by the MPBPWIN program (v 1.43) made available by the U.S. Environmental Protection Agency. This program requires just the input of the chemical structure of the desired compound by SMILES notation and is a scientifically accepted calculation method. The calculation is done by three different methods: Antoine, Modified Grain and Mackay, whereby the Modified Grain method is preferentially utilized. By taking this method into account and using an estimated boiling point of 380.89 °C, pure choline chloride has a vapour pressure of 6.57 * E-8 Pa / 4.93 * E-10 mm Hg at 25 °C (EPIWIN, 2000).

As the substance is marketed as a 75 % aqueous solution, which is therefore the predominantly available form, and it is also directly produced as aqueous solution (no isolation of the solid pure substance), it is justified out of scientific reasons and exposure considerations to regard choline chloride as aqueous solution. Hence, the vapour pressure was calculated using Raoult´s law and an experimental vapour pressure value for water of 3172.5 Pa at 25 °C, resulting in a calculated vapour pressure of 2287.2 Pa at 25 °C. This value is in the scientifically expected range as it is close to the vapour pressure of water.

The outcome of this study is considered reasonable, within the scientifically expected ranges and can be used for further risk assessment.

Due to the reliability of the results, as they were gained by a scientifically accepted calculation method, with regard to the predominantly existing form of choline chloride, i.e. a 75 % aqueous solution, the tonnage-driven requirements under REACH are fully met, no datagaps were identified and no further testing is required.