Determinação de pesticidas em amostras de leite materno por espectrometria de massas ambiente empregando paper spray ionization
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Universidade Federal de Goiás
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The increase in agricultural production in Brazil has driven the excessive and
indiscriminate use of pesticides. These substances are often present, even at trace levels,
in various environmental and food matrices. However, given their widespread
dissemination and persistence in these environments, combined with human exposure to
these residues, they can be detected in different biological fluids, including breast milk.
Due to the complexity of this matrix and the low levels of analytes present, the
development of strategies for sample preparation is necessary to achieve the desired
sensitivity. One strategy to overcome this challenge lies in ambient mass spectrometry
employing the ionization technique known as paper spray ionization (PSI-MS). The PSIMS technique typically uses a triangularly cut chromatographic paper substrate for
sample application. This substrate allows for chemical modifications that can enhance the
sensitivity and selectivity of the desired methods. Modifying the paper using molecularly
imprinted polymers (MIPs) and restricted access materials (RAMs) are promising choices
to improve the sensitivity and selectivity of PSI-MS analyses. MIPs enable highly
selective extraction of target analytes, while RAMs help eliminate endogenous matrix
compounds that could reduce the analytical sensitivity of the PSI-MS approach. Thus, in
this study, MIP and RAM immobilizations were synthesized and characterized to evaluate
their use as modifiers for the paper substrate in PSI-MS applied to pesticide analysis in
breast milk samples. The MIP was synthesized using glyphosate as the template molecule,
methacrylic acid as the functional monomer, diethylene glycol dimethacrylate as the
crosslinking agent, and azobisisobutyronitrile as the radical initiator, under reaction
conditions of 24 hours at 60°C in a nitrogen atmosphere. The RAM was produced using
C-18 particles, onto which bovine serum albumin (BSA) was immobilized on the surface.
The polymers developed were characterized by thermogravimetric analysis/derivative
thermogravimetric analysis-simultaneous differential thermal analysis (TGA/DTGADTA), scanning electron microscopy (SEM), and Fourier-transform infrared
spectroscopy (FTIR). The results confirmed that the materials were obtained as expected.
After characterization, the polymers were immobilized on the paper surface and subjected
to PSI-MS analysis for the determination of glyphosate in breast milk samples. Among
the modifying phases evaluated, the highest analytical sensitivity was obtained using the
RAM phase, which was selected for subsequent tests. The developed PSI-MS method
exhibited linearity in the range of 50 to 600 µg mL⁻¹ with R² = 0.9915. The method's
figures of merit—precision, accuracy, recovery, and matrix effect—were evaluated. The
precision ranged from 1.3% to 8.7%, and recovery ranged from 104.7% to 113.7%.
Preliminary results for glyphosate determination indicated that the synthesized polymers
are promising as modifiers for PSI-MS substrates, allowing the selective determination
of glyphosate in breast milk. Breast milk samples from volunteer patients were analyzed,
and glyphosate was detected at quantifiable levels within the working range in five
samples, with two above the limit of detection (LOD) and one below. In twelve samples,
the analyte was not detected. The developed RAM-PSI-MS methodology proved to be a
promising alternative for glyphosate determination in breast milk samples.
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FERREIRA, P. A. B. Determinação de pesticidas em amostras de leite materno por espectrometria de massas ambiente empregando paper spray ionization. 2024. 63 f. Dissertação (Mestrado em Química) - Instituto de Química, Universidade Federal de Goiás, Goiânia, 2024.