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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:
September 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Study conducted according to OECD 104 and EU A.4 guidelines, under GLP without deviation and with certificate of analysis included.
Reason / purpose:
reference to other study
Reason / purpose:
reference to same study
Reference:
Composition 0
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:
2015-03-05
Type of method:
dynamic method
Remarks:
Knudsen Effusion Method
Test material information:
Composition 1
Test no.:
#1
Temp.:
293.15 K
Vapour pressure:
ca. 2.25 Pa
Remarks on result:
other: First trial
Test no.:
#1
Temp.:
298.15 K
Vapour pressure:
ca. 4.43 Pa
Remarks on result:
other: First trial
Test no.:
#2
Temp.:
293.15 K
Vapour pressure:
ca. 2.08 Pa
Remarks on result:
other: Second trial
Test no.:
#2
Temp.:
298.15 K
Vapour pressure:
ca. 4.1 Pa
Remarks on result:
other: Second trial
Key result
Temp.:
293.15 K
Vapour pressure:
ca. 2.17 Pa
Remarks on result:
other: Mean
Key result
Temp.:
298.15 K
Vapour pressure:
ca. 4.27 Pa
Remarks on result:
other: Mean

First trial:

Mass loss (mg)

Mass loss duration (s)

Vapour pressure (Pa)

Temperature (K)

1/T (K-1)

Log10(p)

0.335

600

3.1866

295.35

3.386E-03

0.5033

0.428

600

4.0904

298.15

3.354E-03

0.6118

0.997

600

9.6223

304.05

3.289E-03

0.9833

2.361

600

23.0325

310.65

3.219E-03

1.3623

5.344

600

52.7667

318.25

3.142E-03

1.7224

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              -5139.4 

Intercept          17.884 

                    0.9978

 

The results obtained indicate the following vapour pressure relationship: 

Log10(p (Pa)) = -5139.4 / T (K) + 17.884

 

The above equation yields a vapour pressure of 2.25 Pa at 293.15 K and 4.43 Pa at 298.15 K.

Second trial:

Mass loss (mg)

Mass loss duration (s)

Vapour pressure (Pa)

Temperature (K)

1/T (K-1)

Log10(p)

0.293

600

2.7871

295.95

3.386E-03

0.4451

0.412

600

3.9375

298.15

3.354E-03

0.5952

0.971

600

9.3729

304.15

3.288E-03

0.9719

2.290

600

22.3506

310.95

3.216E-03

1.3493

5.213

600

51.5217

318.85

3.136E-03

1.7120

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              -5150.2

Intercept          17.887 

                    0.9984

 

The results obtained indicate the following vapour pressure relationship:

Log10(p (Pa)) = -5150.2/ T (K) + 17.887

 

The above equation yields a vapour pressure of 2.08 Pa at 293.15 K and 4.10 Pa at 298.15 K.

Conclusions:
Using the Knudsen Effusion method according to guideline OECD 104 and method EU A.4, vapour pressure of NOPOL is 2.17 Pa at 20°C and 4.27 Pa at 25°C.
Executive summary:

A study was performed to determine the vapour pressure of test item NOPOL. The method followed was designed to be compliant with the OECD Guideline for Testing of Chemicals No. 104, "Vapour Pressure", adopted in March, 2006 and Regulation (EC) No 761/2009, EC A4, 23 July 2009.

In this dynamic method, the mass of the test substance flowing out per unit of time of a Knudsen cell in the form of vapour, through a micro-orifice under ultra-vacuum conditions was determined at various specified temperatures (from 22 to 46°C). The Hertz-Knudsen equation was used to calculate the vapour pressure corresponding to the mass loss rate.

The Log10 (Vapour Pressure (Pa)) was plotted against 1/T (K) and a linear function was obtained. With this equation, the vapour pressure has been calculated for temperatures of 20°C and 25°C.

Two trials were conducted and five points were recorded for each trial.

Log (Vapour Pressure (Pa)) was plotted against reciprocal temperature and values of vapour pressure were calculated at 20°C and 25°C with the linear function parameters (slope and intercept).

Calculated values respect validity criteria (less than 20% of difference) and the linear functions obtained own a correlation coefficient R² over 0.95.

Moreover the calculated values showed good correspondence with the experimentally determined ones.

In conclusion, the vapour pressure of NOPOL is 2.17 Pa at 20°C and 4.27 Pa at 25°C.

Description of key information

The vapour pressure was determined by the Knudsen effusion method (weight loss). 
The vapour pressure of nopol is 2.17 Pa at 20 °C and 4.27 Pa at 25 °C.

Key value for chemical safety assessment

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

Additional information

Key study conducted according to OECD 104 Guideline and EU Method A.4, under GLP without deviation. No observations arousing doubts concerning the accuracy of the results and the validity of the study were made. Therefore, the study was considered as reliable without restriction and the extrapolated vapour pressures at 20 and 25°C can be used as key values.