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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:
2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study performed under GLP. All relevant validity criteria were met.
Qualifier:
according to guideline
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
inspected: July 2012; signature: November 2012
Type of method:
gas saturation method
Temp.:
25 °C
Vapour pressure:
0.868 Pa
Remarks on result:
other: Constituent #1; represents the highest vapour pressure of any constituent determined in the test substance
Temp.:
25 °C
Vapour pressure:
0.037 Pa
Remarks on result:
other: Constituent #2

Calculation of the Vapour Pressure

The vapour pressure of the test item has been calculated for each determination using

 

Pvp = WxRxT / VxM

where:

Pvp = vapour pressure [Pa] (calculated)

W = mass of evaporated test item [ug] (determined by analysis)

R = gas constant= 8.314 J/K mol

T = temperature [K] (measured)

V = volume of nitrogen at test temperature [ mL] (determined from flow rate)

M = molar mass oftest item (components reported in the full study report)

No test item was detected in any trap 2 at any of the temperature ranges, indicating a 100% trapping efficiency in the initial trap 1. Three different flow rates were used to ensure that saturation control was measured at each temperature.

From experimental data performed at the initial three test temperatures, the vapour pressure of the test item at 25 °C was calculated by interpolation of ln vapour pressure versus the reciprocal of test temperature (K) for constituents 1 and 2. Less volatile constituents could only be quantified at a single elevated temperature, therefore interpolation was not possible. The data showed that the higher flow rates did not lead to lower vapour pressures, therefore the nitrogen passing over the test item had become saturated under the conditions of the test. Constituents 1 and 2 were quantified at three different temperatures. Thus interpolation at 25 °C was made based upon this data and the line of best fit it produced. In the absence of any detectable constituents 3 or 4 at 25 °C, 30 °C or 40 °C a limit value was determined at 60 °C (and is presented in the full study report). As only a limit value was achieved even at this elevated test temperature and on applying a 4 day vapour collection period, it was concluded that it was not possible to experimentally determine definitive vapour pressure values for those constituents. Experimental data confirms that for the purpose of regulatory assessment, those constituents are essentially non-volatile, i.e. its vapour pressure less than 7 x 10^-4 Pa at temperatures between 25 °C to 40 °C.

Conclusions:
The vapour pressure of the test substance has been determined to be 0.868 Pa at 25 °C.
Executive summary:

The vapour pressure was determined using EU Method A.4 using the gas saturation method under GLP. To ensure saturation control, three different flow rates were used at each temperature. In the determination higher flow rates did not lead to lower vapour pressures, indicating that the nitrogen was saturated with test substance under the conditions of the test. Two constituents had measurable vapour pressures under the conditions of the study. The highest vapour pressure constituent is reported by the applicant as being reflective of the test item on the basis of that constituent contributing most significantly to saturation of the nitrogen gas phase. The mean vapour pressure was 25°C: 0.828 Pa ; 30°C: 1.32 Pa and 40°C: 2.34 Pa respectively. The vapour pressure of the test substance was extrapolated from the vapour pressure curve (ln Pvp versus 1/T) and was calculated to be 0.868 Pa at 25°C.

Description of key information

Vapour Pressure: 0.868 Pa at 25 °C, EU Method A.4 – gas saturation method, 2014

Key value for chemical safety assessment

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

Additional information

The vapour pressure was determined using EU Method A.4 using the gas saturation method under GLP. To ensure saturation control, three different flow rates were used at each temperature. In the determination higher flow rates did not lead to lower vapour pressures, indicating that the nitrogen was saturated with test substance under the conditions of the test. Two constituents had measurable vapour pressures under the conditions of the study. The highest vapour pressure constituent is reported by the applicant as being reflective of the test item on the basis of that constituent contributing most significantly to saturation of the nitrogen gas phase. The mean vapour pressure was 25°C: 0.828 Pa ; 30°C: 1.32 Pa and 40°C: 2.34 Pa respectively. The vapour pressure of the test substance was extrapolated from the vapour pressure curve (ln Pvp versus 1/T) and was calculated to be 0.868 Pa at 25°C.

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