es062233h_si_001.pdf (91.28 kB)
n-Alkane Profiles of Engine Lubricating Oil and Particulate Matter by Molecular Sieve Extraction
journal contribution
posted on 2007-05-15, 00:00 authored by Gianni A. Caravaggio, Jean-Pierre Charland, Penny Macdonald, Lisa GrahamAs part of the Canadian Atmospheric Fine Particle
Research Program to obtain reliable primary source
emission profiles, a molecular sieve method was developed
to reliably determine n-alkanes in lubricating oils, vehicle
emissions, and mobile source dominated ambient
particulate matter (PM). This work was also initiated to
better calculate carbon preference index values (CPI: the
ratio of the sums of odd over even n-alkanes), a parameter
for estimating anthropogenic versus biogenic contributions
in PM. n-Alkanes in lubricating oil and mobile source
dominated PM are difficult to identify and quantify by gas
chromatography due to the presence of similar components
that cannot be fully resolved. This results in a hump, the
unresolved complex mixture (UCM) that leads to incorrect
n-alkane concentrations and CPI values. The sieve
method yielded better chromatography, unambiguous
identification of n-alkanes and allowed examination of
differences between n-alkane profiles in light (LDV) and
heavy duty vehicle (HDV) lubricating oils that would have
been otherwise difficult. These profile differences made
it possible to relate the LDV profile to that of the PM samples
collected during a tunnel study in August 2001 near
Vancouver (British Columbia, Canada). The n-alkane PM
data revealed that longer sampling times result in a negative
artifact, i.e., the desorption of the more volatile n-alkanes
from the filters. Furthermore, the sieve procedure yielded
n-alkane data that allowed calculation of accurate CPI values
for lubricating oils and PM samples. Finally, this method
may prove helpful in estimating the respective diesel and
gasoline contributions to ambient PM.