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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 11 June 2012 to 16 August 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted in compliance with international standard guidelines under GLP conditions. The study report was well documented with all mandatory information included
Qualifier:
according to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
11-04-11
Type of method:
static method
Temp.:
20 °C
Vapour pressure:
2 320 Pa
Temp.:
25 °C
Vapour pressure:
3 055 Pa

The calculation results are presented in the following table:

n

Temperature T

Pressure P

Temperature T

1/T

log P

 

°C

mbar = hPa

K

1/K

log Pa

1

14.6

16.5

287.75

0.00347524

3.2175

2

19.0

21.5

292.15

0.00342290

3.3324

3

23.8

28.1

296.95

0.00336757

3.4487

4

29.4

38.6

302.55

0.00330524

3.5866

5

39.1

63.7

312.25

0.00320256

3.8041

6

47.0

93.3

320.15

0.00312354

3.9699

7

42.9

74.9

316.05

0.00316406

3.8745

8

34.0

48.8

307.15

0.00325574

3.6884

9

27.3

34.8

300.45

0.00332834

3.5416

10

22.3

27.1

295.45

0.00338467

3.4330

11

17.2

20.7

290.35

0.00344412

3.3160

The parameters for the linear regression of the graph log (p) vs. 1/T are presented in the following table:

Parameter

Value

Slope

-2089.202051

Intercept

10.49219496

Correlation coefficient r

-0.99921712

Using the equations of vapour pressure as function on the temperature the slope and the intercept of graph log P versus 1/T, vapour pressures at ambient temperature and boiling point are calculated. The results are presented in the following table:

Parameter

Value

Unit

Vapour Pressure (20 °C)

2320

Pa

Vapour Pressure (25 °C)

3055

Pa

Boiling Point

380.79

K

Boiling Point

107.64

°C

The vapour pressure of the aqueous solution of the test item was calculated as 2320 Pa at 20.0 °C and 3055 Pa at 25 °C.As the test item is an aqueous solution, a vapour pressure like water, but slightly lower (lowering of vapour pressure according to Raoult’s law) was expected. The vapour pressure of water is 2340 Pa at 20°Cand 3170 Pa at 25 °C. Therefore, the values which were determined in this study are plausible.

Correspondence of the experimental data and the values calculated from the experimental data via equation (result of this study) is very good:

Experimental Data

Values calculated from experimental data

Vapour Pressure (19.0°C)

2150 Pa

Vapour Pressure (20.0 °C)

2320 Pa

Vapour Pressure (23.8°C)

2810 Pa

Vapour Pressure (25.0 °C)

3055 Pa

 Therefore, the result of the study is considered as valid.

Conclusions:
Using the static method, vapour pressures of 2320 Pa at 20 °C and 3055 Pa at 25 °C were determined.
Executive summary:

The determination of the vapour pressure was conducted in accordance with Method No. 104: “Vapour Pressure“ of OECD Guidelines for the Testing of Chemicals, 23 March 2006 and Method A.4: “Vapour Pressure” of Commission Regulation(EC) No 761/2009 of 23 July 2009 and GLP. No deviation from the guidelines were observed during the test.

The study was performed using the static method.In this method, the vapour pressure at thermodynamic equilibrium was determined at a specified temperature. This method is suitable for substances and multicomponent liquids and solids in the range from 10–2to 105Pa.

The vapour pressure of the aqueous solution of the test item was calculated as 2320 Pa at 20.0 °C and 3055 Pa at 25 °C.

Description of key information

Experimental value for test item vapour pressure at 20°C: 2320 Pa
Experimental value for test item vapour pressure at 25°C: 3055 Pa

Key value for chemical safety assessment

Vapour pressure:
130 Pa
at the temperature of:
25 °C

Additional information

The study was conducted in accordance with Method No. 104: “Vapour Pressure“ of OECD Guidelines for the Testing of Chemicals, 23 March 2006 and Method A.4: “Vapour Pressure” of Commission Regulation(EC) No 761/2009 of 23 July 2009 and GLP. No deviation from the guidelines were observed during the test.

The vapour pressure determination was performed on the test item in aqueous solution. Indeed, it is impossible to remove water (by drying) from the commercial product without affecting its composition.

The vapour pressure values found from experimental determination were high: 2320 Pa at 20°C and 3050 Pa at 25°C. These values are likely due to the presence of water in the test item used for the experimental determination. To confirm this assumption, we estimate the vapour pressure of the sample at 25°C by calculation using the Raoult’s law (remaining on the vapour pressure of the main components in the test item and their content).

The Raoult’s law states that the vapour pressure of an ideal solution is equal to the vapour pressure of each chemical component weighted by the mole fraction of the components present in the solution. The law is summarized by the following equation:

Pi = Sum(Psi * xi)

With   Pi: the vapour pressure of the test item

Psi: vapour pressure of component i

xi: mole fraction in the sample of the component I in the liquid phase

The vapour pressure of the MAEEU (N-[2-(2-Oxoimidazolidin-1- yl)ethyl]methacrylamide) at 25°C was found by a QSAR (EPIWEB 4.1, MPBPWINTMprogram). The vapour pressure value from methacrylic acid was found in MPBPWINTMprogram database. This value was determine experimentally (DAUBERT,TE & DANNER,RP (1997)). The vapour pressure value at 25°C for water was found in Internet database (http://intro.chem.okstate.edu/1515sp01/database/vpwater.html). The values found were in accordance with HRC handbook 71Stedition 1990-1991. The mole fraction is calculated by the Molar mass and the mass fraction. The equation used is: xi = [Mass fraction of i compound in test item / Molar mass of i compound] / [Sumni=1(Mass fraction i compound / Molar mass i compound)]

Compound

Molar Mass (g/mol)

Mass fraction in the test item (%)

Mole fraction in the test item (%)

Vapour pressure of the pure compound at 25°C (Pa)

Vapour pressure (Pi) in the test item (Pa)

M.A.E.E.U

197

47.3

11.7

0.0000219

Methacrylic acid

86

24.4

13.8

130

18

Water

18

27.5

74.5

3120

2323

Aqueous solution of test item

119

99.2

100

-

2341

The calculated vapour pressure of the test item at 25°C is close to the experimental value found: 2341 Pa vs 3050 Pa. The difference observed between the two values could be explained by the approximation of the Raoult’s law. Indeed, the law is defined for ideal solution that is not the case for the test item solution used.

Based on the results obtained in the table above, we can assume that the main part of the vapour pressure of the test item is due to the presence of water and a low part to methacrylic acid.

The methacrylic acid is classified as “Harmful if swallowed” (Acute Tox. 4 H302) according to its REACH registration dossier. The vapour pressure of this substance in the test item is low but not negligible. Consequently it was decided to use the vapour pressure value of this substance as a key value for test item aqueous solution as a worst case scenario. The vapour pressure of methacrylic acid at 25°C is considered at 130Pa.