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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a (Q)SAR model, with limited documentation / justification, but validity of model and reliability of prediction considered adequate based on a generally acknowledged source
Justification for type of information:
QSAR prediction
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: W.J. Lyman, W.F. Reehl and D.H. Roosenblatt, Handbook of chemical property estimation methods. American Chemical Society, chapter 14, 1990
Qualifier:
according to
Guideline:
other: W.J. Lyman. Environmental exposure from chemicals. Vol 1 Chapter 2, 1985
Principles of method if other than guideline:
The method makes use of estimating the heat of vaporisation at the boiling temperature, from which the vapour pressure is calculated. Three different QSARs are used in the derivation of the vapour pressure, based on the same dataset. The model automatically gives a suggested vapour pressure for the compound of interest. For liquids (like DBPP) typically the average of the Antoine and the modified grain method is reported as the suggested vapour pressure
Type of method:
other: QSAR
Temp.:
20 °C
Vapour pressure:
0.002 Pa

The accuracy of the method was tested on a database containing 3037 different compounds. Some of which had similar structures as DBPP. A plot of preferred experimental values against measured data gave an R2 of 0.914 and a std dev of 1.057 (avg std 0.644).

There is no well defined applicability domain, however when the vapour pressure drops below 0.13 mPa the estimation error decreases. As the estimate for DBPP equals 0.00186 Pa this is not the case. Also the molecular weight of DBPP lies well within the MW range of the substances present in the database.

Conclusions:
The vapour pressure of DBPP at 20 °C is estimated to be 0.00186 Pa
Executive summary:

The vapour pressure was estimated using QSARs described in EPISuite vs 4.10. In this approach three different QSARs are used to estimate the vapour pressure and the final selected vapour pressure is the one calculated according to the modified Grain method.

The QSAR is well described and established. It is based on a large dataset containing over 3000 different compounds and has excellent values for R2 and std dev for experimental results plotted against estimated results.

The estimated value for the vapour pressure of DBPP equals 0.00186 Pa.

Description of key information

The vapour pressure DBPP (mono-constituent) was estimated using QSARs described in EPISuite vs 4.10. With this approach, three different QSARs are used to estimate the vapour pressure. The final selected vapour pressure is the one calculated according to the modified grain method. The QSAR is well described and established as it is based on a large dataset containing over 3000 different compounds and has excellent values for R2 and std dev for experimental results plotted against estimated results.  The estimated value for the vapour pressure of DBPP equals 0.00186 Pa. Additionally, this QSAR was also run for the two other constituents of DBPP resulting in the following order of decreasing vapour pressure: TBP > DBPP > BDPP. 

Key value for chemical safety assessment

Vapour pressure:
0.002 Pa
at the temperature of:
20 °C

Additional information

The reaction mass of DiButyl Phenyl Phosphate (DBPP) also contains ca. 10% Tri Butyl Phosphate (TBP) and ca 20% Butyl DiPhenyl Phosphate (BDPP) and 70% DiButyl Phenyl Phosphate (DBPP).

For all three compounds a QSAR was run to estimate the vapour pressure. The QSAR is well defined, based on elaborate training and validation datasets and all three compounds fall well within the applicability domain of the QSAR:

Compound: Vapour pressure (Pa)

DBPP: 0.00186

TBP: 0.466

BDPP: 0.000232

As DBPP is the main component the VP of DBPP was selected for further risk assessment purposes.