Agriculture Reference
In-Depth Information
Figure 7.5.
Principle of high-resolution full scan screening using a nontargeted approach with semi-
quantitative differential expression analysis. Reproduced with permission from Anses - Euroreference
Journal.
outputresults,wewereabletoidentifysome of the suspected ions (metabolites
of drugs) in the microbial inhibition-active beef muscle sample. As an example,
N
4-acetylsulfadimethoxine, a metabolite of the sulfadimethoxine antimicrobial,
was identi
ed using this approach in a beef sample, in addition to the presence of
sulfadimethoxine. Furthermore, MS/MS experiments of suspected [M
H]
+
ions
were carried out in order to get structural information. Finally, some of the
suspected analyte ionic structures were con
+
rmed unambiguously by comparing
the mass spectral data with reference standards synthetically prepared. At our
laboratory, this type of analysis has since been repeated on muscle samples of
various species like beef, pork, poultry, and rabbit. The detection of drug metabo-
lites in animal tissues offers undoubted evidence of the administration of the parent
drug to the animal.
The same method is now being applied to identify trace amounts of unknown
antimicrobials in meat samples when these samples are screened showing positive
microbial inhibition activity. In these samples, none of the known antibiotics, at least
from those that were used at our laboratory, were identi
ed by either MRM/SRM or
high-resolution full scan MS.
This approach is time consuming for a unique sample to be screened thoroughly and
is not successful for a certain number of samples. Nontargeted screening of ions of
interest present only in the positive sample and not in the set of blank samples is highly
difficult, especiallywhen the concentration is not high enough for the instrument to get a
signi
cant signal (lack of sensitivity for residual traces of substances). If such
techniques could be streamlined, however, the potential to screen for dozens of
compounds in a single LC
-
HRMS analysis would signi
cantly increase the throughput
