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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 14,2012 to February 08, 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
The result has been considered as reliable without restriction because the test was performed in compliance with OECD and EU guidelines giving scientifically valid results. All measured values show very good reproducibility, giving relative standard deviations of less than 10%, and good correlation. No observations arousing doubts concerning the accuracy of the results and the validity of the study were made.
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Version / remarks:
(2006)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.4 (Vapour Pressure)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
effusion method: by loss of weight or by trapping vaporisate
Key result
Temp.:
ca. 20 °C
Vapour pressure:
ca. 1.33 Pa
Key result
Temp.:
ca. 25 °C
Vapour pressure:
ca. 2.63 Pa

Measurement data at 30°C:

The data of the evaluated experiments is presented in the following tables:

Experiment

1

 

 

 

 

Nom. Temperature

30 °C

 

 

 

 

Date and time START

 

20.Sep.2012

17:45

21. Sep.2012

17:00

22. Sep.2012

09:30

23. Sep.2012

09:02

Date and time END

 

21. Sep.2012

13:45

22. Sep.2012

08:30

23. Sep.2012

08:05

24. Sep.2012

09:40

Parameter

Weight m

Weight m

Weight m

Weight m

Weight m

Unit

g

g

g

g

g

Knudsen-cell 1

4.16361

4.37718

4.20459

3.96271

3.70286

Knudsen-cell 2

4.13449

4.29576

4.11586

3.86001

3.58477

Knudsen-cell 3

4.08471

4.30459

4.13531

3.89143

3.62423

Knudsen-cell 4

4.04869

4.33803

4.17223

3.92462

3.65577

Measurement Data at 45°C :

Experiment

2

 

 

 

Nom. Temperature

45 °C

 

 

 

Date and time START

 

25.Sep.2012 17:45

26. Sep.2012 09:35

26. Sep.2012 12:30

Date and time END

 

26. Sep.2012 07:55

26. Sep.2012 12:00

26. Sep.2012 15:45

Parameter

Weight m

Weight m

Weight m

Weight m

Unit

g

g

g

g

Knudsen-cell 1

4.45065

3.35264

3.17935

2.96654

Knudsen-cell 2

4.44508

3.38713

3.22735

3.02574

Knudsen-cell 3

4.40290

3.36453

3.19914

2.99089

Knudsen-cell 4

4.42146

3.38528

3.21993

3.01644

Observations: after three measurement series at 30°C, the cells were almost empty. Therefore, the test was continued with freshly filled cells at 45°C. After the measurements at 45°C, the test item was almost completely evaporated again and the test was finished.

Calculation Results :

All calculation results are given in the tables below:

Experiment

1

 

 

 

 

 

 

 

 

 

 

 

Real Temperature in K

303.2

 

 

 

 

 

 

 

 

 

 

 

Real Temperature in

°C

30.0

 

 

 

 

 

 

 

 

 

 

 

Date of Measurement

21.09.2012 13:45

22.09.2012 08:30

23.09.2012 08:05

24.09.2012 09:40

Elapsed Time in s

72000

55800

81300

88680

Parameter

Weight loss

to be used

Vapour pressure

Weight loss

to be used

Vapour pressure

Weight loss

to be used

Vapour pressure

Weight loss

to be used

Vapour pressure

Unit

g

yes/no

Pa

g

yes/no

Pa

g

yes/no

Pa

g

yes/no

Pa

Knudsen-cell 1

-0.21357

no

 

0.17259

yes

5.21E+00

0.24188

yes

5.01E+00

0.25985

yes

4.94E+00

Knudsen-cell 2

-0.16127

no

 

0.17990

yes

5.43E+00

0.25585

yes

5.30E+00

0.27524

yes

5.23E+00

Knudsen-cell 3

-0.21988

no

 

0.16928

yes

5.11E+00

0.24388

yes

5.06E+00

0.26720

yes

5.08E+00

Knudsen-cell 4

-0.28934

no

 

0.16580

yes

5.01E+00

0.24761

yes

5.13E+00

0.26885

yes

5.11E+00

Mean

 

 

 

 

yes

5.19E+00

 

 

5.13E+00

 

 

5.09E+00

Standard deviation:

 

 

 

 

 

1.82E-01

 

 

1.28E-01

 

 

1.20E-01

Mean of measured values:

 

5.135E+00

 

 

 

 

 

 

 

 

 

Standard deviation:

 

5.188E-02

RSD:

 1.0%

 

 

 

 

 

 

 

If “no” is stated in the respective column: measurement was not considered for the calculation of the mean. The “first” measurement series at

30°C was not used for evaluation as the measurements at 30°C had to be started again with fresh cells.

Experiment

2

 

 

 

 

 

 

 

 

Real Temperature in K

318.2

 

 

 

 

 

 

 

 

Real Temperature in °C

45.0

 

 

 

 

 

 

 

 

Date of Measurement

26.09.2012 07:55

26.09.2012 12:00

26.09.2012 15:45

Elapsed Time in s

51000

8700

11700

Parameter

Weight loss

to be used

Vapour pressure

Weight loss

to be used

Vapour pressure

Weight loss

to be used

Vapour pressure

Unit

g

yes/no

Pa

g

yes/no

Pa

g

yes/no

Pa

Knudsen-cell 1

1.09801

yes

3.72E+01

0.17329

yes

3.44E+01

0.21281

yes

3.14E+01

Knudsen-cell 2

1.05795

yes

3.58E+01

0.15978

yes

3.17E+01

0.20161

yes

2.97E+01

Knudsen-cell 3

1.03837

yes

3.51E+01

0.16539

yes

3.28E+01

0.20825

yes

3.07E+01

Knudsen-cell 4

1.03618

yes

3.51E+01

0.16535

yes

3.28E+01

0.20349

yes

3.00E+01

Mean

 

yes

3.58E+01

 

yes

3.29E+01

 

yes

3.05E+01

Standard deviation:

 

 

9.70E-01

 

 

1.10E+00

 

 

7.42E-01

Mean of measured values:

 

3.307E+01

 

 

 

 

 

 

Standard deviation:

 

2.665E+00

RSD:

 8.1%

 

 

 

 

Evaluation :

The measured values for temperature and vapour pressure were evaluated as follows:

Parameter

T

P

1/T

log p

Unit

K

Pa

1/K

log Pa

Values

303.2

5.14E+00

3.2982E-03

0.7106

318.2

3.31E+01

3.1427E-03

1.5194

For these two temperatures, 1/T was plotted against log (P).The plotted graph 1/T vs. log (P) shows a straight line with a correlation coefficientof - 1.0000 as only two temperatures could be evaluated.

Parameters of the linear regression :

Parameter

Value

Slope

-5202.4

Intercept

17.8690

Correlation Coefficient r

-1.0000

y = -5202.4x + 17.869 (R² = 1)

Results:

The following vapour pressures were determined experimentally and considered as valid (mean and standard deviation given):

T

T

P

Stand. Dev. P

RSD P

°C

K

Pa

Pa

%

30.0

303.2

5.14E+00

5.19E-02

1.0%

45.0

318.2

3.31E+01

2.67E+00

8.1%

For the test item nopyl acetate, the following vapour pressures at 20 °C and at 25 °C were calculated from the regression equation:

Vapour pressure at 20 °C:

1.33Pa

Vapour pressure at 25 °C:

2.63Pa

The linear regression of log p vs. 1/T gave a correlation coefficient r of - 1.0000 as only two temperatures could be evaluated.

Conclusions:
The vapour pressure of nopyl acetate was determined as 1.33 Pa at 20 °C and 2.63 Pa at 25 °C.
Executive summary:

The vapour pressure of nopyl acetate was determined at two different temperatures (30 and 45°C) following EU Method A.4 using the effusion method (weight loss).

First, the determination was performed at 30 °C.

As the apparatus had to be cleaned due to contamination with bubbled over test items and too much test item was already evaporated, freshly filled cells were used for the measurements at 30°C. After three measurement series at 30 °C, the test item was evaporated almost completely. Therefore, the test was continued at 45°C with freshly filled cells and measurement intervals less than 24 hours after consultation of the monitor because the weight loss at 45 °C was too high for the usual time interval of one day. The measured data showed good correlation; therefore, this had no negative influence on the determination.

At each temperature, four knudsen cells were prepared and analysed in the same way.

All measured values show very good reproducibility, giving relative standard deviations of less than 10%, and good correlation. Due to the high volatility of the test item no measurement at more than 45 °C were conducted. The vapour pressure of nopyl acetate was 1.33 Pa at 20°C and 2.63 Pa at 25°C.

Note: the vapour pressure lies in the limit range between the effusion method (10-10 to 1 Pa) and the static method (10 to 105 Pa). Even if the static method is theoretically applicable for vapour pressures of 1 to 10 Pa, this method can be difficult to be performed with terpenes and error-prone in lower pressure ranges as well. Therefore, the effusion method, which was approved in the range of 1 - 5 Pa in some cases, was conducted. As the weight loss was very good reproducible at both temperatures, the result was considered as reliable.

No observations arousing doubts concerning the accuracy of the results and the validity of the study were made. Therefore the result of the test can be considered valid.

Description of key information

The vapour pressure was determined by the effusion method (weight loss). 
The vapour pressure of nopyl acetate is 1.33 Pa at 20 °C and 2.63 Pa at 25 °C.

Key value for chemical safety assessment

Vapour pressure:
1.33 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 for chemical safety assessment.

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