24
A. G. RYDER
Recently, in NUI-Galway, fluorescence lifetime data has been acquired from a series
of HCFI and correlated with data obtained from a test set of 23 crude oils.
32 The HCFI
all emitted similar coloured fluorescence under 405 nm excitation, however, all were
clearly discriminated on the basis of their lifetime measurements. Unfortunately, the
study also showed that the fluorescence lifetimes of some HCFI oils were much longer
than the lightest oils in the text set. This is probably because the oils in HCFI contain
higher fractions of light hydrocarbon liquids and gases that are not present in the bulk oils
sampled. This will necessitate the development of larger calibration datasets, which
comprise of non-topped crude oils (or analogues) to account for the gases and volatiles
entrapped in HCFI. It will be also necessary to fabricate artificial HCFI with entrapped
oils of known compositions to further validate the methodology. Artificial HCFI can be
synthesised in halite
77 at low temperature, and more recently from quartz at higher
temperature.
78 Unfortunately, it is not clear that it will be possible to have a well defined
(known chemical composition) oil in these HCFI as there is evidence that partitioning
and/or thermal degradation can occur.
450
500
550
600
650
700
2
4
6
8
10
12
14
(A)
average lifetime[ns]
wavelength[nm]
F3a
F6b
F6d
F8a
JP1
450
500
550
600
650
700
2
4
6
8
(B)
average lifetime[ns]
wavelength[nm]
7058
7098
7703
Figure 19: Plot of average fluorescence lifetime versus emission wavelength for: A) HCFI samples, B) several
light crude oils, API gravity = 50.6˚ - 40.1˚. Reproduced with permission from Ref. [32] © 2004, Society for
applied Spectroscopy.
The use of lifetime based measurements for HCFI characterization, while still in its
infancy does offer considerable benefits when compared to the more traditional colour,
intensity, and spectral measurements. Finally, one novel application of fluorescence to
inclusion studies involves using confocal microscopy to measure the volume of oil and
gas within fluid inclusions by utilising the spatial resolution of modern confocal
microscopes.
79
6. APPLICATIONS: REMOTE SENSING/OIL SPILL IDENTIFICATION
Oil spill identification is another area where fluorescence based methods are being
applied.
80, 81 The development of laser fluorosensors for oil spill identification was
recently reviewed by Fingas, concentrates on ship-borne and airborne sensors using 308
A. G. RYDER
Recently, in NUI-Galway, fluorescence lifetime data has been acquired from a series
of HCFI and correlated with data obtained from a test set of 23 crude oils.
32 The HCFI
all emitted similar coloured fluorescence under 405 nm excitation, however, all were
clearly discriminated on the basis of their lifetime measurements. Unfortunately, the
study also showed that the fluorescence lifetimes of some HCFI oils were much longer
than the lightest oils in the text set. This is probably because the oils in HCFI contain
higher fractions of light hydrocarbon liquids and gases that are not present in the bulk oils
sampled. This will necessitate the development of larger calibration datasets, which
comprise of non-topped crude oils (or analogues) to account for the gases and volatiles
entrapped in HCFI. It will be also necessary to fabricate artificial HCFI with entrapped
oils of known compositions to further validate the methodology. Artificial HCFI can be
synthesised in halite
77 at low temperature, and more recently from quartz at higher
temperature.
78 Unfortunately, it is not clear that it will be possible to have a well defined
(known chemical composition) oil in these HCFI as there is evidence that partitioning
and/or thermal degradation can occur.
450
500
550
600
650
700
2
4
6
8
10
12
14
(A)
average lifetime[ns]
wavelength[nm]
F3a
F6b
F6d
F8a
JP1
450
500
550
600
650
700
2
4
6
8
(B)
average lifetime[ns]
wavelength[nm]
7058
7098
7703
Figure 19: Plot of average fluorescence lifetime versus emission wavelength for: A) HCFI samples, B) several
light crude oils, API gravity = 50.6˚ - 40.1˚. Reproduced with permission from Ref. [32] © 2004, Society for
applied Spectroscopy.
The use of lifetime based measurements for HCFI characterization, while still in its
infancy does offer considerable benefits when compared to the more traditional colour,
intensity, and spectral measurements. Finally, one novel application of fluorescence to
inclusion studies involves using confocal microscopy to measure the volume of oil and
gas within fluid inclusions by utilising the spatial resolution of modern confocal
microscopes.
79
6. APPLICATIONS: REMOTE SENSING/OIL SPILL IDENTIFICATION
Oil spill identification is another area where fluorescence based methods are being
applied.
80, 81 The development of laser fluorosensors for oil spill identification was
recently reviewed by Fingas, concentrates on ship-borne and airborne sensors using 308