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Vapour pressure

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 Dec 2021 - 07 Feb 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 104 (Vapour Pressure Curve)

Version / remarks:

March 23, 2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

Version / remarks:

July 23, 2009

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

effusion method: isothermal thermogravimetry

Key result

Temp.:

20 °C

Vapour pressure:

< 0 Pa

Temp.:

25 °C

Vapour pressure:

< 0 Pa

Conclusions:

The vapour pressure of the test item was determined to be <8.4 e-7 Pa at 20 °C and < 6.2e-7 at 25 °C

Reference 2

Endpoint:

vapour pressure

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
Estimation Programs Interface Suite™ for Microsoft® Windows v4.11. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

2. MODEL (incl. version number)
MPBPWIN v1.43 (September 2010)

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
C[C@H](N)C(N[C@H](C(O)=O)CSSC[C@@H](C(O)=O)NC([C@@H](N)C)=O)=O
CAS: 115888-13-6
Melting point: 240°C (decomposition temperature)

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL

- Defined endpoint:
vapour pressure

- Unambiguous algorithm:
Antoine Method: Chapter 14 of Lyman et al (1990) includes the description of the Antoine method used by MPBPWIN. It was developed for gases and liquids. The Antoine equation used to estimate vapor pressure from the normal boiling (Tb) is shown in the attached document. MPBPWIN has extended the Antoine method to make it applicable to solids by using the same methodology as the modified Grain method to convert a super-cooled liquid VP to a solid-phase VP as shown below.
Modified Grain Method: Chapter 2 of Lyman (1985) describes the modified Grain method used by MPBPWIN. This method is a modification and significant improvement of the modified Watson method. It is applicable to solids, liquids and gases. The modified Grain method equations are shown in the attached document.
Mackay Method: The equation derived by Mackay to estimate VP (Lyman, 1985) is shown in the attached document.
All three methods use the normal boiling point to estimate VP. Unless the user enters a boiling point on the data entry screen, MPBPWIN uses the estimated boiling point from the adapted Stein and Brown method (For more information see: Stein, S.E. and Brown, R.L. 1994. Estimation of normal boiling points from group contributions. J. Chem. Inf. Comput. Sci. 34: 581-7). MPBPWIN reports the VP estimate from all three methods. It then reports a "suggested" VP. For liquids and gases, the suggested VP is the average of the Antoine and the modified Grain estimates. The Mackay method is not used in the suggested VP because its application is currently limited to its derivation classes.

- Defined domain of applicability:
Currently there is no universally accepted definition of model domain. However, users may wish to consider the possibility that property estimates are less accurate for compounds outside the Molecular Weight range of the training set compounds, and/or that have more instances of a given fragment than the maximum for all training set compounds. It is also possible that a compound may have a functional group(s) or other structural features not represented in the training set, and for which no fragment coefficient was developed. These points should be taken into consideration when interpreting model results.
Training Set Molecular Weights:
Minimum MW: 16.04
Maximum MW: 943.17
Average MW: 194.22

- Appropriate measures of goodness-of-fit and robustness and predictivity:
The accuracy of MPBPWIN's "suggested" VP estimate was tested on a dataset of 3037 compounds with known, experimental VP values between 15 and 30 deg C (the vast majority at 25 or 20 deg C). The experimental values were taken from the PHYSPROP Database that is part of the EPI Suite. For this test, the CAS numbers were run through MPBPWIN as a standard batch-mode run (using the default VP estimation temperature of 25 deg C) and the batch estimates were compared to PHYSPROP's experimental VP.

- Mechanistic interpretation:
MPBPWIN estimates vapor pressure (VP) by three separate methods: (1) the Antoine method, (2) the modified Grain method, and (3) the Mackay method. For more detailed information about the methodologies please refer also to Lyman, W.J. 1985. In: Environmental Exposure From Chemicals. Volume I., Neely,W.B. and Blau,G.E. (eds), Boca Raton, FL: CRC Press, Inc., Chapter 2. and Lyman, W.J., Reehl, W.F. and Rosenblatt, D.H. 1990. Handbook of Chemical Property Estimation Methods. Washington, DC: American Chemical Society, Chapter 14.

5. APPLICABILITY DOMAIN

- Descriptor domain:
Molecular weight

- Similarity with analogues in the training set:
The substance consists of several fragments which are all present in the training data sets. Moreover, based on molecular weight the substance also falls into the applicability domain of the model.


6. ADEQUACY OF THE RESULT
The estimation is based on i.a. melting point and experimental data (Differential Scanning Calorimetry) revealed that the substance has no melting point but decomposes instead. However, since the substance falls into the molecular weight range predictivity of the model used, the prediction is considered to be sufficient to provide reliable results for classification and labelling and/or risk assessment. Furthermore, the vapour pressure obtained from the QSAR prediction is very low which substantiates the assumption that testing of vapour pressure is technically not feasible.

For further informations on the model used please refer to the attached justification.

Qualifier:

no guideline followed

Principles of method if other than guideline:

QSAR prediction performed with EPISuite software /MPBPWIN v 1.43 (Spetember 2010).

GLP compliance:

no

Type of method:

other: QSAR estimation method

Test no.:

#1

Temp.:

25 °C

Vapour pressure:

0 Pa

Remarks on result:

other: Result from QSAR estimation

SMILES : CC(N)C(=O)(NC(C(=O)(O))CSSCC(C(=O)(O))NC(=O)(C(N)C))

CHEM  : N,N’-di-L-alanyl-L-cystine / (L-Ala-L-Cys)2

MOL FOR: C12 H22 N4 O6 S2

MOL WT : 382.45

------------------------ SUMMARY MPBPWIN v1.43 --------------------

Vapor Pressure Estimations (25 deg C):

 (Using BP: 709.34 deg C (estimated))

 (Using MP: 240.00 deg C (user entered))

   VP:          1.24E-023 mm Hg (Antoine Method)

     :              1.65E-021 Pa (Antoine Method)

   VP:          4.44E-016 mm Hg (Modified Grain Method)

     :             5.92E-014 Pa (Modified Grain Method)

   VP:          1.43E-015 mm Hg (Mackay Method)

     :              1.91E-013 Pa (Mackay Method)

 Selected VP:        4.44E-016 mm Hg (Modified Grain Method)

            :                  5.92E-014 Pa (Modified Grain Method)

 Subcooled liquid VP:      9.38E-014 mm Hg (25 deg C, Mod-Grain method)

                    :                     1.25E-011 Pa (25 deg C, Mod-Grain method)

Conclusions:

According to EPISuite/MPBPWIN v 1.43 the vapour pressure of N,N'-di-L-Alanyl-L-cystine is 5.92E-014 Pa at 25°C.

Description of key information

Vapour pressure: < 8.4e-7 Pa at 20 °C (OECD 104, GLP)

Key value for chemical safety assessment

Vapour pressure:

0 Pa

at the temperature of:

20 °C

Additional information

According to OECD Test Guideline 104 (2006) and Regulation (EC) No 440/2008 Method A.4., the Vapour pressure of the test item N,N’-di-L-alanyl-L-cystine / (L-Ala-L-Cys)2 at 20 ° is:

<8.4e-7 Pa.