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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:
30 November 2016 and 6 December 2016
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The study was conducted according to an internationally recognised method, and under GLP. Restrictions apply considering the complex nature of the substance and the interpretation of the result. The substance is considered to be adequately characterised. Therefore validation with restrictions applies.
Qualifier:
according to
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Version / remarks:
2006
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.4 (Vapour Pressure)
Version / remarks:
2009
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)
Remarks:
inspected on 1,2 and 3 July 2014 / signed on 5 Mars 2015
Type of method:
static method
Temp.:
20 °C
Vapour pressure:
1 061 Pa
Key result
Temp.:
25 °C
Vapour pressure:
1 362 Pa

First trial

 

Vapour Pressure (Pa)

Time      (hh:mn)

Corresponding Temperature (°C)

Temperature (K)

1/T (K-1)

Log10(p)

950

10:50

19.3

292.45

3.419E-03

2.978

1280

12:00

23.7

296.85

3.369E-03

3.107

1676

13:40

28.3

301.45

3.317E-03

3.224

2075

15:05

32.7

305.85

3.270E-03

3.317

2480

16:50

37.3

310.45

3.221E-03

3.394

 

A plot of Log10(p) versus reciprocal temperature (1/T) (with p in Pa and T in K) gives the following statistical data using an unweighted least square treatment.

 

Slope             -2107.5

 

Intercept         10.199

 

                   0.992

 

The results obtained indicate the following vapour pressure relationship:

 

Log10(p (Pa)) = -2107.5 / T (K) +10.199

 

The above equation yields an interpolated vapour pressure of 1024 Pa at 293.15 K and 1351 Pa at 298.15 K.

Second trial

Vapour Pressure (Pa)

Time      (hh:mn)

Corresponding Temperature (°C)

Temperature (K)

1/T (K-1)

Log10(p)

1065

10:45

19.2

292.35

3.421E-03

3.027

1260

11:25

23.4

296.55

3.372E-03

3.100

1570

12:25

28.0

301.15

3.321E-03

3.196

1935

13:45

32.7

305.85

3.270E-03

3.287

2260

15:00

37.0

310.15

3.224E-03

3.354

A plot of Log10(p) versus reciprocal temperature (1/T) (with p in Pa and T in K) gives the following statistical data using an unweighted least square treatment.

 

Slope              -1697.3

 

Intercept         8.8302

 

                   0.9986

 

The results obtained indicate the following vapour pressure relationship:

 

Log10(p (Pa)) = -1697.3 / T(K) + 8.8302

 

The above equation yields an interpolated vapour pressure of 1098 Pa at 293.15 K and 1373Pa at 298.15 K.

Summary of Results

 

Trial

Vapour pressure at 293.15 K

Vapour pressure at 298.15 K

1

1024 Pa

1351 Pa

2

1098 Pa

1373 Pa

Mean

1061 Pa

1362 Pa

 

For the two determinations, the test item did not change in appearance since its first heating at 40°C. However, it may be noted traces of bubbles at the surface of the test item.

Discussion

Five pairs temperature/pressure were used to define a linear regression, from which vapour pressure at 20°C and 25°C could be estimated. The test was performed in duplicate.

The study is conducted in a closed system and the protocol was established taking into account the complex nature of the substance.

- The measurement range was limited to remain in a linearity range.

- The tested temperatures were similar to temperatures currently used in the handling of the substance.Therefore no significant chemical reactions should be considered in the experimental conditions;

- We take care to obtain an homogenous mass and to allow any bubbles in the sample to come to the surface prior measurement and measurements are below 40°C. Therefore no impact of residual air was anticipated and

- We take care to minimally alter the composition of the complex substance, i.e. to consider the most volatile constituents as part of the composition of the UVCB substance in the measurements.

Finally, the correlation factor of the regression equations for log10(p)=f(1/T) was over 0.95 for the both trials (0.992 for the first trial and 0.9982 for the second trial).

The difference between the two trials at 25°C was less than 20% (7% at 20°C and 1.6% at 25°C).

Therefore, the results of this study are considered valid.

Executive summary:

The vapour pressure of the test item was measured under GLP using the static method as described in EU method A.4 and OECD 104.

Two trials were conducted and five points were recorded for each trial in a temperature range of 19.2 – 37.3 °C. The pairs of Temperature / Vapour pressure were used to calculate a regression from which vapour pressure at ambient temperature can be interpolated.

Finally, the vapour pressure of the test item was calculated as 1061 Pa at 20°C and 1362 Pa at 25°C.

 

Note that the result obtained on this kind of substance should be largely influence by small amounts of volatile constituents and these values don't represent the major part of the substance. Therefore the result should be considered with caution when used for subsequent assessment (worst case).

Description of key information

The vapour pressure of the test item was calculated as 1061 Pa at 20°C and 1362 Pa at 25°C (interpolation)

Note that the result obtained on this kind of substance should be largely influence by small amounts of volatile constituents and these values don't represent the major part of the substance. Therefore the result should be considered with caution when used for subsequent assessment (worst case).

Key value for chemical safety assessment

Vapour pressure:
1 362 Pa
at the temperature of:
25 °C

Additional information

A reliable experimental study conducted according to a recognized OECD/EC method and under GLP, is available.

Therefore it is considered as a key study and the result is retained as key data.