Environmental Engineering Reference
In-Depth Information
35
30
25
Birds of Prey
Companion animals
Others
Bait
20
15
10
5
0
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
Figure 6.4
Type and number of specimens that tested positive for carbofuran between 1997
and 2009
tandem mass spectrometry (LC/MS/MS). Electron (EI) impact is the ionisation technique most
commonly used for GC/MS and electrospray ionisation (ESI) is most commonly used for LC/
MS. These techniques are employed exclusively by us for the determination of multiple-res-
idues of a wide range of chemicals (including carbofuran and its metabolites) in a variety of
matrices such as liver, kidney, bait, biological fl uid, digestive tract material, and suspicious
chemicals and substances.
The specifi c LC/MS/MS transitions: m/z 222 → m/z 165 and m/z 222 → m/z 123 are moni-
tored throughout a designated time-scheduled data acquisition window, and used in conjunction
with chromatographic retention time information to determine the presence of carbofuran in extracts
from various samples associated with suspected poisoning incidents. The peak areas of the cor-
responding ion chromatograms are measured and quantifi ed against a multi-point calibration curve
generated following identical analysis of a set of calibration standards that cover an appropriate
carbofuran concentration range (typically 0.01 mg/ml to 5 μg/ml).
Figure 6.5 shows the 'overlain' LC/MS/MS ion chromatogram (i.e., mouth content, stomach con-
tent and proximate 2 μg/ml calibration standard) relating to the positive determination of carbofuran
in extracts from the mouth and stomach contents of a poisoned golden eagle (
Aquila chrysaetos
(inset in Figure 6.5)) found dead in Tayside, Scotland in June 2009. Golden eagles are afforded the
highest protection status in the UK (3) and Scotland
(4), and this particular incident received nation-
wide multi-media attention
(5).
Following non-routine inspection of mass spectral data in a carbofuran positive sample,
isofenphos was also found to be present. The data had been acquired using GC/MS in full-scan
mode. Interrogation of the data revealed an unexpected background chromatographic peak, and
subsequent spectral library searches indicated that the organophosphorus insecticide isofenphos was
a 'top match'. This combination of carbofuran and isofenphos was signifi cant, because the latter has
never been approved for use in the UK. This suggests that the poison used in this case contained
both compounds. When archived samples that had previously tested positive for carbofuran were
re-analysed, some of these also tested positive for isofenphos.
Granular product formulations containing both substances, at 4.0% w/w (i.e., weight per weight)
carbofuran and 2.0% w/w isofenphos, do exist. Such products, i.e., 'Yaltox-Combi' (refer back to
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