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Vapour pressure

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Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
supporting study
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
EPI Suite version 4.11

2. MODEL (incl. version number)
Mpbpwin v. 1.43

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.
Qualifier:
according to
Guideline:
other: REACH Guidance on QSARs R.6
Principles of method if other than guideline:
- Software tool(s) used including version: EPI Suite v4.11
- Model(s) used: Mpbpwin Model version 1.43
The model estimates vapour pressure by three different methods:
- the Antoine equation (Lyman WJ, Reehl WF and Rosenblatt DH. 1990. Handbook of Chemical Property Estimation Methods. Washington, DC: American Chemical Society);
- the Modified Grain Method (Lyman WJ. 1985. In: Environmental Exposure From Chemicals. Volume I. Neely WB and Blau GE (eds). Boca Raton, FL: CRC Press, Inc., Chapter 2);
- the Mackay Method (Lyman WJ. 1985. In: Environmental Exposure From Chemicals. Volume I. Neely WB and Blau GE (eds). Boca Raton, FL: CRC Press, Inc.).
MPBPWIN selects a “suggested” vapour pressure: the modified Grain for solids and the average of the Antoine and the modified Grain for liquids and gases.
A dataset of 3037 compounds with experimentally determined vapour pressure values has been used to evaluate the model (using the “suggested” values as outcome), giving a correlation coefficient of 0.914. The evaluation clearly shows that the model reliability decrease for vapour pressure below 0.0001 Pa.
The dataset contains 1642 compounds with available experimental Boiling points and Melting points. The correlation coefficient evaluated on this subset (0.949) indicates that VP estimates are more accurate when experimental BP and MP are available.

- Model description: see field 'Justification for type of information', 'Attached justification' and 'any other information on Material and methods'
- Justification of QSAR prediction: see field 'Justification for type of information', 'Attached justification' and/or 'overall remarks'
GLP compliance:
no
Type of method:
other: QSAR
Temp.:
25 °C
Vapour pressure:
0 Pa
Remarks on result:
other: Modified Grain method

QSAR result; transition/decomposition is not specified/reported. For detailed description of the model and its applicability, see "Any other information on materials and methods incl. tables”

Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
26 - 28 Nov 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 830.7950 (Vapor Pressure)
Deviations:
no
GLP compliance:
yes
Type of method:
effusion method: isothermal thermogravimetry
Temp.:
20 °C
Vapour pressure:
<= 0.001 Pa
Temp.:
25 °C
Vapour pressure:
<= 0.001 Pa

Results

 

The equation of the curve was: log PT = -4887 x 1/T + 13.50 (r = 0.991, n = 6).

 

Results of the Vapour pressure Isothermal TGA Analysis

Temperature
[°C]

Weight loss
[µg/min]

νT
[g/cm2/h]

log νT

log PT

PT
[Pa]

120

6.21823

7.42E-4

-3.13

1.10

13

 

5.66169

6.76E-4

-3.17

1.05

11

130

10.9158

1.30E-3

-2.89

1.41

26

 

9.67671

1.16E-3

-2.94

1.34

22

140

18.9507

2.26E-3

-2.65

1.71

51

 

16.5859

1.89E-3

-2.70

1.64

43

 

Vapour Pressure of the Test Item

Temperature
[°C]

log PT

PT
[Pa]

PT
[mm Hg]

20

-3.17

6.8E-4

5.1E-6

25

-2.89

1.3E-3

9.7E-6

 

 

Conclusion

The isothermal TGA effusion method was applied for the determination of the vapour pressure of the test item.

The vapour pressure of the test item at 20 °C (293K) and 25 °C (298K) was:

 

20 °C

25 °C

[Pa]

[mm Hg]

[Pa]

[mm Hg]

Test item

≤ 6.8E-4

≤ 5.1E-6

≤ 1.3E-3

≤ 9.7E-6

 

 

The weight losses of the test item were obtained with a temperature program of above the melting temperature of the test item. According to this, the vapour pressure of the test item (which was, according to the method, extrapolated to 20 °C and 25 °C) could be slightly overestimated.

Description of key information

Vapour pressure: ≤6.8E-4 at 20 °C, ≤1.3E-3 at 25 °C (OECD Guideline 104, effusion method: isothermal thermogravimetry)

Key value for chemical safety assessment

Additional information

A vapour pressure of 9.98E-8 Pa was estimated with the Mpbpwin QSAR model, using the modified grain method. This result is used to support the low vapour pressure of the tested substance.