Agriculture Reference
In-Depth Information
of enro
oxacin (2
μ
g/kg) was higher than the LOQ of TOF
-
MS and QqQ
-
MS/MS and
around the LOQof Q
MSwas
a feasible alternative to Q and QqQ in multiresidue analysis in food samples.
A recent study attempted to determine the mass resolution and corresponding mass
window width required with HRMS techniques to obtain selectivity comparable to
that of MS/MS [56]. They investigated the
-
MS. Therefore, the results indicated that the use of TOF
-
available in MS/MS
and HRMS spectra of an analyzed blank sample. The idea behind this concept was the
assumption that monitoring a large number of such randomly selected masses shows a
number of traces containing one or more chromatographic peaks caused by endog-
enous matrix compounds. The measurement of the number and the intensity of the
detected peaks provides information regarding the degree of selectivity obtained by
the analyzer. To carry out this comparison, 100 dummy transitions and exact masses
(traces) were created by a random generator and monitored in blank extracts of
“
vacant
m
/
z
space
”
fish, kidney, liver, and honey by UHPLC
-
QqQ
-
MS/MS and UHPLC-single-stage
Orbitrap
MS. With this last analyzer, different resolution power and mass window
were applied (10,000 FWHM:20 mDa, 25,000 FWHM:8mDa, 50,000 FWHM:4
mDa, and 100,000 FWHM:2mDa). Although these dummy transitions did not
correspond to any particular analyte, they corresponded to the typical precursor
and product ion mass range, as commonly observed for VDs. As expected, most
extracted dummy traces were free of chromatographic peaks, but the dummy traces
that contained chromatographic peaks were integrated. In the next step, the SRM and
HRMS peak areas obtained were standardized. This was done by determining the
response of seven typical VDs (peak area/concentration), and an average response for
all these analytes was calculated. Then, each dummy peak area was divided by this
average response to produce a standardized concentration for each matrix-related
dummy peak area. This was done for MS/MS and HRMS. As a result of these
experiments, the authors concluded that a HRMS resolution of 50,000 FWHM and a
corresponding mass window of 10 ppm provide selectivity as good as or slightly
higher than MS/MS. Moreover, the false positive found in a sample of honey, when it
was analyzed by MS/MS technique, supported their conclusion.
The same authors evaluated the general quantitative and con
-
rmative performance
of MS/MS against the latest generation of Orbitrap
-
MS and TOF
-
MS technol-
ogy [105,117]. First, they compared UHPLC-single-stage Orbitrap
-
MS operated at
50,000 FWHM with UHPLC
cation of anthelmintic drugs
and phenylbutazone residue in milk and muscles [105]. The results showed that
repeatability of both technologies were equal, but signi
-
QqQ
-
MS/MS for quanti
cantly higher sensitivity was
obtained for critical compounds (avermectins) by single-stage Orbitrap detection. The
LODs obtained with single-stage Orbitrap
-
MS were 0.5
μ
g/kg in milk and from 0.5 to
2
μ
g/kg in muscles, whereas LODs for QqQ
-
MS/MS ranged from 0.5 to 10
μ
g/kg in
milk and from 1 to 10
g/kg in muscle samples. Therefore, it was shown that analytes
with poor fragmentation properties (e.g., sodium-cationized molecules), such as
avermectin and ivermectin, can be more easily quanti
μ
ed by single-stage HRMS
than by MS/MS.
In the second of these studies [117], the quantitative performance of HRMS-based
detection (a single-stage Orbitrap
-
MS operated at 50,000 FWHM and a TOF
-
MS
