Agriculture Reference
In-Depth Information
samples, the analytes were con
rmed using the data obtained by the fragmentation of
the native ions in the HCD collision cell. The authors showed the ability of HRMS
detectors to acquire with and without fragmentation in the HCD collision cell, and
therefore the possibility of performing the screening and con
rmation with a single
injection.
Finally, the ability of the proposed method was tested to quantify the con
rmed
analytes showing good quantitative results for all the studied analytes. The linearity
for all VDs was acceptable in a range of concentrations from 5 to 100
μ
g/kg, showing
cients (
R
2
) higher than 0.98. The limit of quanti
determination coef
cation was
g/kg for milk- and powdered milk-based formula samples, except for spiramycin
in powdered milk-based formula (Table 6.2), being in all cases lower than the MRLs
established by the EU.
Once the applicability of UHPLC-coupled single-stage Orbitrap
5
μ
MS technique
was demonstrated for the analysis of target and nontarget compounds, Kaufmann
et al. [104] tried to go beyond these applications by developing a semitargeted
screening of VDs (112 target VDs and 116 posttarget VDs) in
-
fish samples by UHPLC
single-stage Orbitrap
MS with a chromatographic run time of 14 min. In this work,
qualitative and quantitative analyses of the 112 targeted analytes were based on the
traditional approach of target analysis by external standards. However, different
procedures were developed for the detection of 116 additional compounds, which
were monitored without having access to reference materials. This additional data
evaluation can be classi
-
ed as a posttargeted analysis of VDs. First, the detection
procedure was based on theoretical exact masses and narrow mass windows (10 ppm)
because one can include posttarget analytes considering that the elemental composi-
tion is known and ionization is adequate. Although the XICs were extracted using
narrow mass windows, some matrix components interfered in the determination of the
selected compounds. Therefore, any signal observed in the chromatogram could
potentially be the compound. The measurement of accurate masses and relative
isotopic abundance (RIA) of suspected peaks was then applied. None of the 116
monitored compounds could be detected in the investigated samples using this
strategy. In consequence, other alternatives were tested, such as the search for
generic product ions characteristic of certain VD families; speci
c
software, which searches for a particular RIA in the entire chromatographic time and
mass scan range; and speci
c RIA by speci
c neutral losses. Any of these searching strategies were
clearly feasible for the posttarget study proposed, and, consequently, the authors
emphasized that the evaluated procedures still showed some limitations for their
application in posttarget analysis.
The IT technology has been used for identi
rmation of VD
residues in food samples, but only a few works have focused on the development
of screening methods. Among these studies, the method proposed by Baiocchi
et al. [109], in which they describe a screening and con
cation and con
rmation method to monitor
eight synthetic corticosteroids in bovine liver tissues employing LC
MS, can be
highlighted. In this work, selected ion monitoring (SIM) and SRM detection modes
were checked and compared, concluding that the best sensitivity was obtained in
MS/MS mode (Table 6.3). In a different study, Heller et al. [110] demonstrated the
-
IT
-
