GULFTENE C16-18 ISOMERISED OLEFINS - NICNAS

Comments on Physico-Chemical Properties
Test reports were available only for C20 – C24 alkenes, branched and linear, which is similar
to Gulftene 16-18, but consists of higher molecular weight alkenes. The tests were conducted
in facilities that complied with OECD Principles of Good Laboratory Practice (GLP), and
based on methods that complied with OECD test guidelines and or EC Directive 92/69/EEC
(OECD 1995-1996), (European Commission 1992).
Water solubility was also determined for the C20-24 blend. The solubility was determined by
shaking aliquots of the chemical (approximately 0.1g) with 500 mL of distilled water at 30°C,
and allowing these to stand and equilibrate at 20°C for more than 24 hours. The aqueous
phase was then centrifuged, filtered and analysed for the compound using gas
chromatography. The concentration of the mixture of C20-24 blend in water at 20°C was less
than 17.5 µg/L (mean of three determinations). Gulftene 16-18 contains lower molecular
weight fractions than the C20-24 alkene mixture for which the water solubility was
determined. Accordingly, the water solubility for Gulftene 16-18 may be slightly higher than
that for the C20-24 blend. However, low water solubility would be expected for hydrocarbon
compounds of this nature.
The vapour pressure of C20-24 alkenes branched and linear was determined using a vapour
pressure balance based on the iseniscope method conducted by (Safepharm Laboratories
Limited 1998), whereby a linear relationship is obtained from a plot of the logarithm of the
equilibrium vapour pressure versus reciprocal temperature. This linear relation was
determined on three separate samples of the material, and one typical result was –
Log10 [vapour pressure (Pa)] = 4180/Temperature (K) + 12.2
The mean vapour pressure at 25°C from three such linear determinations gives a vapour
pressure of less than 0.000017 kPa at 25°C. However, the tabulated result is for the C20-24
mixture, and accordingly the measured vapour pressure is probably weighted towards that of
the more volatile (lower molecular weight) components. It is probable that Gulftene 16-18
has a significantly higher vapour pressure than that indicated above because it consists of
lower molecular weight components. In support of this, the OECD Screening Information
Data Set (OECD 1992) for tetradecene gives the vapour pressure for this compound at 25°C
as 0.0019 kPa.
The Henry’s Law Constant is a measure of the degree of partitioning of a compound between
the aqueous phase and the atmosphere and is calculated according to the relationship –
H = Vapour pressure (Pa) x Molecular weight (g/mole)/Water solubility (g/m 3 ).
Taking the water solubility as 20 µg/L, the vapour pressure as 1.7 x10 -5 kPa and using a
molecular weight of 200 g/mole an estimate for H (at 25°C) is around 200 Pa m 3 /mole.
However, it is likely that various components of Gulftene 16-18 will have higher vapour
pressures and would also have different (but still small) water solubilities. Consequently,
while this value for H may be an underestimate, it is clear that the material would be
appreciably volatile and tend to partition from the water phase to the atmosphere.
FULL PUBLIC REPORT 26 April 2000
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