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Vapour pressure

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Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 16 May 2012 to 25 January 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to same study
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:
2012-12-15
Type of method:
effusion method: vapour pressure balance
Remarks:
Knudsen effusion cell
Key result
Temp.:
20 °C
Vapour pressure:
0 Pa
Transition / decomposition:
no

Results:

A first assay was made; the mass of sample weighed was 2.59 mg. The sample was placed in a Knudsen effusion cell with an aperture size of A = 279.9 μm. Then the cell was placed in the apparatus. Temperature steps at 40, 45 and 50 °C were made but no loss of mass was recorded. A second assay was made; the mass of sample weighed was 4.89 mg. The sample was placed in a Knudsen effusion cell with an aperture size of A = 279.9 μm. Then the cell was placed in the apparatus. Temperature steps at 70 and 85 °C were made but no loss of mass was recorded. A third assay was made; the mass of sample weighed was 4.41 mg. The sample was placed in a Knudsen effusion cell with an aperture size of A = 279.9 μm. Then the cell was placed in the apparatus.

The temperature was increased up to about 110 °C in order to detect a loss of mass. This temperature step was taken into account.

Another temperature step at 120 °C was made but no linear loss of mass was recorded.

The temperature was increased up to 130 and then 140 °C and these steps were taken into account. The test item (powder) was compacted after the experimentation. No degradation of the test item was observed.

The vapour pressure of the test item was calculated by the “Knudsen software”. The calculation results are summarized in the following table.

Test temperature t (°C) Test temperature T (K) 1/T (K-1) Experimental vapour pressure P (Pa) Log P (Pa) Knudsen effusion cell size (μm)
110 383.15 2610*10-3 9.3932*10-3 -2.027 279.9
130 403.15 2480*10-3 6.9995*10-2 -1.155
140 413.15 2420*10-3 2.0173*10-1 -0.695

The molecular weight of Cocamidopropyl Hydroxysultaine (C12 acyl chain) is 422.6 g/mol.

The graph log P = f (1/T) was then plotted to extrapolate the vapour pressure at 20 °C (see Attachment 1).

Conclusions:
The vapour pressure of the test item extrapolated at 20 °C was 0.000000023 Pa.
Executive summary:

The vapour pressure of the test item (= substance EC 939-455-3) was investigated in a GLP-compliant study performed in accordance with OECD Guideline 104 (Vapour Pressure Curve) and EU Method A.4 (Vapour Pressure) using the effusion method. The vapour pressure of the test item was 2.3x10-8 Pa at 20°C (extrapolated value). The test item is considered as not volatile.

Endpoint:
vapour pressure
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
C8-C18 AAPHS and C12-18 AAPHS have the same functional groups, and general composition. The main variable resides in the alkyl chain distribution.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source chemical = C8-18 cocamidopropyl hydroxysultaine (EC 939-455-3).
Target chemical = C12-18 cocamidopropyl hydroxysultaine (EC 939-457-4).

3. ANALOGUE APPROACH JUSTIFICATION
The alkyl C-chain distribution of the source chemical significantly overlaps with the one of the target chemical, the C12-alkyl derivative being the major constituent in both chemicals. The structural differences in side C-chains is not expected to lead to significant differences on phys-chem properties.

4. DATA MATRIX
See "Documentation and scientific justification of the read-across approach" in section 13.2.
Reason / purpose:
read-across source
Key result
Temp.:
20 °C
Vapour pressure:
0 Pa
Remarks on result:
other: read-across from EC 939-455-3
Transition / decomposition:
no
Conclusions:
By analogy with the source substance EC 939-455-3, a vapour pressure of 2.3E-8 Pa at 20°C was reported for the target substance 1-Propanaminium, N-(3-aminopropyl)-2-hydroxy-N,N-dimethyl-3-sulfo-, N-(C12-18(even numbered) acyl) derivs., hydroxides, inner salts (EC 939-457-4).

Description of key information

As the vapour pressure of the substance EC 939-457-4 has not been determined experimentally, a read-across approach was followed to fill in the endpoint. The vapour pressure of a structural analogue substance (= source substance EC 939-455-3) was investigated in a GLP-compliant study (Ricau, 2013) performed in accordance with OECD Guideline 104 (Vapour Pressure Curve) and EU Method A.4 (Vapour Pressure) using the effusion method. The vapour pressure of the analogue substance was 2.3E-8 Pa at 20°C (extrapolated value). By analogy, a vapour pressure of 2.3E-8 Pa at 20°C was reported for the target substance 1-Propanaminium, N-(3-aminopropyl)-2-hydroxy-N,N-dimethyl-3-sulfo-, N-(C12-18(even numbered) acyl) derivs., hydroxides, inner salts (EC 939-457-4).

The alkyl C-chain distribution of the source substance EC 939-455-3 significantly overlaps with the one of the target substance EC 939-457-7, the C12-alkyl derivative being the major constituent in both chemicals. The structural differences in side C-chains is not expected to lead to significant differences on phys-chem properties.

Key value for chemical safety assessment

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

Additional information

The vapour pressure of the structural analogue substance (= source substance EC 939-455-3) was investigated in a GLP-compliant study (Ricau, 2013) performed in accordance with standard methods, without deviations. The study is considered as reliable (Klimisch 1) and was selected as key study for the endpoint of the target substance EC 939-457-4.