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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:
22 February - 01 March 2018
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
iSafeRat® HA-QSAR toolbox v1.1

2. MODEL (incl. version number)
iSafeRat® HA-QSAR v 1.3 to predict Vapour Pressure

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
SMILES code (see attached QPRF)

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached QMRF

5. APPLICABILITY DOMAIN
See attached QPRF

6. ADEQUACY OF THE RESULT
See attached QPRF
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
yes
Remarks:
QSAR model
Principles of method if other than guideline:
A Quantitative Structure-Property Relationship (QSPR) model was used to calculate the vapour pressure of the constituents of the test item. This QSPR model has been validated as a QSAR model to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004) and predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following Guideline for Testing of Chemicals No. 104, "Vapour Pressure". The criterion predicted was the vapour pressure at 25°C in Pascals.

The determination was performed using a regression method in which validated boiling point values are plotted against the log of vapour pressure values, where the pressure is in Pascals. The comparison was made with other members of the same chemical group. The results are considered to be as accurate as those from a good quality OECD guideline 104 study.
GLP compliance:
no
Type of method:
other: QSAR
Key result
Test no.:
#1
Temp.:
25 °C
Vapour pressure:
0.392 Pa
Remarks on result:
other: constituent 1
Key result
Test no.:
#2
Temp.:
25 °C
Vapour pressure:
7.91 Pa
Remarks on result:
other: constituent 2
Key result
Test no.:
#3
Temp.:
25 °C
Vapour pressure:
0.227 Pa
Remarks on result:
other: constituent 3
Key result
Test no.:
#4
Temp.:
25 °C
Vapour pressure:
0.051 Pa
Remarks on result:
other: constituent 4
Key result
Test no.:
#5
Temp.:
25 °C
Vapour pressure:
0.617 Pa
Remarks on result:
other: constituent 5
Key result
Test no.:
#6
Temp.:
25 °C
Vapour pressure:
0.316 Pa
Remarks on result:
other: constituent 6

The results below are the vapour pressure values of 6 constituents of the substance (covering more than 94% of the composition), which can be anticipated during a study following the OECD Guideline No. 104. The vapour pressure values are calculated as follows:

Constituents 

vapour pressure (Pa) at 25 °C

95% confidence limits (Pa)

constituent 1

0.392

0.314 – 0.488

constituent 2

7.91

7.50 – 8.34

constituent 3

0.227

0.182 – 0.283

constituent 4

0.0513

0.0474 – 0.0555

constituent 5

0.617

0.495 – 0.770

constituent 6

0.316

0.254 – 0.394

Conclusions:
The vapour pressures of 6 constituents of the test item were estimated based on a valid QSAR as follows:

Constituents : vapour pressure (Pa) at 25 °C (95% confidence limits (Pa))
Constituent 1 : 0.392 Pa (0.314-0.488 Pa)
Constituent 2 : 7.91 Pa (7.50-8.34 Pa)
Constituent 3 : 0.227 Pa (0.182-0.283 Pa)
Constituent 4 : 0.0513 Pa (0.0474-0.0555 Pa)
Constituent 5 : 0.617 Pa (0.495-0.770 Pa)
Constituent 6 : 0.316 Pa (0.254-0.394 Pa)
Executive summary:

A calculation method prediction was performed to assess the vapour pressure of 6 constituents of the substance. This calculation method predicts the endpoint value which would be expected when testing a pure substance under experimental conditions in a laboratory following Guideline for Testing of Chemicals No. 104.

The estimation method is based on a linear regression equations for a series of common structures (for example alkanes) generated using high quality vapour pressure data. In the majority of cases data for vapour pressure were obtained from the following methods described in the OECD Guideline No. 104: isoteniscope, dynamic, static, effusion (vapour pressure balance or loss of weight) and gas saturation methods. Likewise, data for boiling points were obtained from the following methods described in the OECD Guideline No. 103: DSC (Differential Scanning Calorimetry), DTA (Differential Thermal Analysis), dynamic method, capillary (Siwoloboff) method, ebulliometer, distillation and photocell detection.

Finally the vapour pressures of 6 constituents of the test item (covering more than 94% of the composition) were estimated in a range between 0.0513 and 7.91 Pa at 25°C.

Description of key information

The vapour pressure of the constituents of the substance (6 components of the substance covering more than 94% of the composition) are in the range between 0.0513 and 7.91 Pa at 25°C (valid QSAR estimations).

Key value for chemical safety assessment

Additional information

No study was conducted on the test item itself.

The test item is a natural complex substance (NCS). It is a mixture of several constituents, but 6 of them represent more than 94% of that mixture.

This calculation method predicts the endpoint value which would be expected when testing a pure substance under experimental conditions in a laboratory following Guideline for Testing of Chemicals No. 104. The criterion predicted was the vapour pressure in Pa at 25°C.

The vapour pressures of the constituents of the substance were estimated at 25°C as follows:

Constituents 

vapour pressure (Pa) at 25 °C

95% confidence limits (Pa)

constituent 1

0.392

0.314 – 0.488

constituent 2

7.91

7.50 – 8.34

constituent 3

0.227

0.182 – 0.283

constituent 4

0.0513

0.0474 – 0.0555

constituent 5

0.617

0.495 – 0.770

constituent 6

0.316

0.254 – 0.394

The substance is an UVCB with constituents having different vapour pressures. In addition we can not anticipate the impact of the interactions between the constituents and the influence of the physical state of the substance on the whole substance vapour pressure.

Therefore we considered the vapour pressure of the 6 constituents of the substance and no single key value was retained (nor calculated weighted Vapour pressure nor worst-case).