Biology Reference
In-Depth Information
Figure 5.12
E coli
Raman spectra. Source:
Reproduced from Fig. 4 in Ref.
51
.
speciation between three species of
Cryptosporidium
:
C. parvum
,
C. hominis
and
C. meleagridis
to the subspecie level, and it was observed that fresh oocysts
(a few months old) and old oocysts (older than 12 months) had different
fingerprints (
Fig. 5.13
).
52
A significant drawback of SERRS is the long data
acquisition time, typically 15-20 min per oocyst depending on the range of
wavelengths used. Coherent anti-Stokes Raman spectroscopy (CARS) offers
acquisition of a
Cryptosporidium
oocyst in just a few seconds
53
and these
authors suggest that this would enable near real-time processing of oocysts
in a water sample (assuming a preconcentration step). A patent has also been
published related to a Raman-based method for assessing the occurrence
of
Cryptosporidium
in a water sample and claiming the possibility of differ-
entiating between viable and nonviable oocysts.
54
No LOD was reported.
Giardia
detection is also mentioned in the patent
54
as well as by Rule et al.
55
(
Fig. 5.13
).
To alleviate the bulkiness of current Raman spectroscopy instruments,
researchers have reported successful attempts to miniaturize probes,
56
and
handheld Raman spectrometers are commercialized by several companies,
including Horiba Scientific (2011), Intevac (2011) and Gammadata (2011).
Development of portable systems is covered in a recent review that exam-
ined forensic and homeland security applications.
57
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