Agriculture Reference
In-Depth Information
was carried out by measuring accurate mass and retention time, but additionally, the
con
rmation was based on accurate mass measurements of their fragment ions,
obtaining mass errors
MS
method showed excellent sensitivity for the studied analytes, with LODs ranging from
0.06 to 7.00
2 ppm in most cases. The optimized UHPLC
-
TOF
-
<
g/kg, demonstrating enough sensitivity to be applied for quantitative
trace analysis (Table 6.1). Finally, it was applied to real samples and it allowed the
detection and quanti
μ
cation of benzalkonium chloride-C
12
in one sample. Another
interesting publication [61] described a quantitative method for 100 VDs in meat
matrices by UHPLC
first fully validated quantitative method
covering a high number of analytes. It allowed the identi
-
TOF
-
MS. This was the
cation of
a wide range of VDs with different polarity and p
K
values (benzimidazoles,
quinolones, lincomycin, macrolides, nitroimidazoles, penicillins, sulfonamides, tet-
racyclines, tranquilizers, and others). However, it was not able to detect other
compounds such as chloramphenicol, nitrofurans, and aminoglycosides, and quantify
other apolar drugs such as benzimidazoles, avermectins, and ionophores; this fact was
then supported by the validation procedure, and consequently, the authors concluded
that UHPLC
cation and quanti
MS was not ideal for the measurement at very low concentrations
of certain banned drugs. Taking into account the results obtained after trying some
extraction and cleanup protocols, the authors questioned the initial euphoria that
UHPLC-TOF-MS would be able to detect and quantify an unlimited number of drug
residues. However, this method could detect and quantify other analytes that had
MRL values at 100 or even 1000
-
TOF
-
g/kg (Table 6.1). Additionally, bearing in mind the
high number of analyses that were needed to carry out the validation, they showed the
need for rede
μ
ning validation guidelines for multiresidue methods, which cover
hundreds of compounds.
An additional approach developed by the same authors was based on the use of
single-stage Orbitrap
-
MS analyzer operating at 50,000 FWHM [53]. The resolution
power (
MS technology was not selective enough for
monitoring low residue concentrations for some compounds in the studied matrices;
this was the main reason adduced to increase mass resolution. When liver and kidney
extracts obtained according to the previous validated multiresidue method were
analyzed by a single-stage Orbitrap
15,000 FWHM) of TOF
-
<
MS analyzer, extensive signal suppression was
observed. The phenomenon was termed postinterface signal suppression, because the
suppression of signals did not occur in the electrospray interface but in the C-trap
device. Thus, a low analyte concentration can be easily detected in a pure standard,
but it can no longer be reliably detected in a dirty matrix sample. It is important to note
that the reported postinterface signal suppression affects only the intensity of low-
mass ions, but does not cause mass shifts of the affected ions. This problem was
partially
-
fixed by a more extensive protein removal step. As a consequence, the
proposed sample cleanup had to be intensi
ed by more extensive deproteination steps,
and instrumental settings had to be reoptimized to eliminate these suppression effects.
Finally, the resulting method proved to be capable of detecting all analytes included in
the original TOF
cantly better performance (e.g.,
linearity, reproducibility, and detection limits) was obtained (Table 6.2). Although
the average recovery was lower than that obtained for the previous TOF
-
MS-based method, and signi
-
MS-based
