Fig. 6 illustrates the chromatogram obtained for the homogenized
apple spiked at the 1g/mL concentration level. The two
unidentified peaks were found in all the analyzed samples.
Chromatograms relative to homogenized pear and plum, perfectly
comparable to the one illustrated in Fig. 6, are not reported.
In order to complete the investigation, homogenized zucchini
containing olive oil (2.5%), was also subjected to analysis, in order
to evaluate the applicability of the method to fatty foods. Pesticide
recoveries ranged from 30 to 40% in most cases, but was
lower than 16% for the most retained peaks, demonstrating that the
appliedmethodwas not suitable for this kind of matrix. As recently
reported [34], the presence of lipids (that cause lower sensitivity
and a shorter column life)would have required amodification of the
method, with the introduction of an additional step, for their elimination
from the sample; consequently, fatty foods were excluded
from the investigation.
4. Conclusions
Anano-LC/UVmethod has been developedand optimizedfor the
analysis of eight organophosphorus pesticides in baby foods. Three
capillary columns were packed with different stationary phases in
order to find the most selective chemistry for the separation of the
target compounds.
The column packed with PinnacleTM II Phenyl offered the best
results in terms of chromatographic performance, and was chosen
as the most suitable for the experiment.
The issue of low sensitivity, typically observed in miniaturized
techniques, was overcome by on-column focusing of large injection
volumes, that enabled a sensitivity increase of almost 100-fold
(LODs, 4.4–37.5 ng/mL).
After 500 runs of standard solutions and real-world samples,
with the same capillary column, the overall analytical
performance showed no evident changes, demonstrating that
the lab-constructed column offered great stability, durability and
robustness.
The validated method was applied to the analysis of a series of
baby foods, previously spiked with the OPPs standard mixture. The
combination of LLE and SPE clean-up resulted to be the best choice,
generating chromatogramswith fewinterferences. Recovery values
were acceptable for all compounds, except for those characterized
by low water solubility. Objectives of future studies could be the
improvement of the recovery values reported and to extend and
verify the suitability of the proposed method for the trace analysis
of different pesticides in various real-world matrices.
Acknowledgements
K.B. is deeply grateful to Dr. Salvatore Fanali, Dr. Zeineb Aturki
and Dr. Anna Rocco for their precious support during the stay at the
Institute of Chemical Methodologies of the CNR.
Fig. 6 illustrates the chromatogram obtained for the homogenized
apple spiked at the 1g/mL concentration level. The two
unidentified peaks were found in all the analyzed samples.
Chromatograms relative to homogenized pear and plum, perfectly
comparable to the one illustrated in Fig. 6, are not reported.
In order to complete the investigation, homogenized zucchini
containing olive oil (2.5%), was also subjected to analysis, in order
to evaluate the applicability of the method to fatty foods. Pesticide
recoveries ranged from 30 to 40% in most cases, but was
lower than 16% for the most retained peaks, demonstrating that the
appliedmethodwas not suitable for this kind of matrix. As recently
reported [34], the presence of lipids (that cause lower sensitivity
and a shorter column life)would have required amodification of the
method, with the introduction of an additional step, for their elimination
from the sample; consequently, fatty foods were excluded
from the investigation.
4. Conclusions
Anano-LC/UVmethod has been developedand optimizedfor the
analysis of eight organophosphorus pesticides in baby foods. Three
capillary columns were packed with different stationary phases in
order to find the most selective chemistry for the separation of the
target compounds.
The column packed with PinnacleTM II Phenyl offered the best
results in terms of chromatographic performance, and was chosen
as the most suitable for the experiment.
The issue of low sensitivity, typically observed in miniaturized
techniques, was overcome by on-column focusing of large injection
volumes, that enabled a sensitivity increase of almost 100-fold
(LODs, 4.4–37.5 ng/mL).
After 500 runs of standard solutions and real-world samples,
with the same capillary column, the overall analytical
performance showed no evident changes, demonstrating that
the lab-constructed column offered great stability, durability and
robustness.
The validated method was applied to the analysis of a series of
baby foods, previously spiked with the OPPs standard mixture. The
combination of LLE and SPE clean-up resulted to be the best choice,
generating chromatogramswith fewinterferences. Recovery values
were acceptable for all compounds, except for those characterized
by low water solubility. Objectives of future studies could be the
improvement of the recovery values reported and to extend and
verify the suitability of the proposed method for the trace analysis
of different pesticides in various real-world matrices.
Acknowledgements
K.B. is deeply grateful to Dr. Salvatore Fanali, Dr. Zeineb Aturki
and Dr. Anna Rocco for their precious support during the stay at the
Institute of Chemical Methodologies of the CNR.
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