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Physical & Chemical properties

Vapour pressure

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Description of key information

Vapour pressure

Key value for chemical safety assessment

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

Additional information

A GLP study was carried out according to recognised guideline. However, the results observed are not representative of the expectations for vapour pressure for this type of substance. The phosphates as a group do not demonstrate vapour pressures at the level noted within the study. One justification for this is the methodology used. OECD 104 provides a variety of measuring methods for the vapour pressure parameter. 

However, the Isoteniscope method utilised in this study is only suitable for substances with a vapor pressure range of 10E+02 to 10E+05 Pa. This method should not be used to determine vapor pressure of substances with expected low levels of volatility, such as is noted in analogue materials. The high results obtained in this study are unreliable due to the method’s non-applicable range of vapor pressure.

Data is available on analogous substances as follows:

Tri-o-tolyl phosphate as a structural analogue of tris(methylphenyl)phosphate details an extrpolated vapour pressure of 0.00195 Pa at 25°C.

 

Diphenyl tolyl phosphate as a structural analogue of tris(methylphenyl)phosphate details a vapour pressure of <1.2 x 10-4 Pa at 25°C

 

QSAR assessment of the components of the substance details the following results:

 

US EPA On-Line EPI Suite™ MPBPWIN v1.43

 

Estimated Vapour Pressure (Pa) – Grain Method

tri-m-tolyl phosphate

3-Methylphenyl di-4-methylphenyl Phosphate

4-Methylphenyl di-3-methylphenyl phosphate

< 0.00111

< 0.00111

< 0.00111

Estimated Vapour Pressure (Pa) – Antoine Method

0.000235

0.000235

0.000235

 

Note: The boiling point value for the study is given as > 400°C. However, the US EPA On-Line EPI Suite™ MPBPWIN v1.43 does not allow use of limit values. MPBPWIN estimates vapor pressure (VP) by the Antoine method and the modified Grain method, using the normal boiling point. Therefore the Grain method cited provides a value of < 0.00111 Pa for all 3 components. As such, the Antoine method is utilised as the definitive value overall for the vapour pressure of each substance, and this is given as 0.0002 Pa. 

 

 

US EPA (T.E.S.T) v4.1

 

Estimated Vapour Pressure (Pa)

tri-m-tolyl phosphate

3-Methylphenyl di-4-methylphenyl Phosphate

4-Methylphenyl di-3-methylphenyl phosphate

0.000049

0.000057

0.0000499

 

On the basis of the analogue data and the QSAR derivations, it is deemed appropriate to utilise the higher of the two QSAR values for vapour pressure for the purposes of hazard assessment. As such, the QSAR values derived using the US EPA On-Line EPI Suite™ MPBPWIN v1.43are used as the base value.

 

Finally, the study was repeated using Knudsen effusion method (mass-loss technique), according to the guidelines OECD 104 / EU A.4. Based on the results, the vapor pressure of the compound is calculated as being equal to 4.7 x 10-6 Pa (4.7 x 10-8 mbar) at 20 °C, and 2.3 x 10-4 Pa (2.3 x 10-6 mbar) at 50 °C. As discussed within the weight of evidence approach above, these results demonstrate that the substance is not sufficiently volatile to be of concern.