Development of an analytical method for the determination of pesticides
in tropical fruits based on combination of QuEChERS extraction and
dispersive liquid-liquid microextraction by LC-QTOF-MS/MS
Abstract
Rationale: Pesticides are poisonous substances or mixtures of
dangerous chemicals used to prevent, dissuade, control, or eradicate
insects, weeds, rodents, fungi, or other potentially dangerous
organisms. Pesticides must be separated from complex matrices before
analysis by performing the proper extraction, cleaning, and/or
preconcentration processes. The QuEChERS method served as a matrix
clean-up tool and the DLLME method preconcentrated the analytes for
their determination at trace levels. To increase the detection
efficiency, a simple and efficient pretreatment process is required.
Method: In this study, QuEChERS extraction was combined with
dispersive liquid-liquid microextraction (DLLME) to extract pesticides
from tropical fruits for determination by a highly accurate and
sensitive liquid chromatography-quadrupole time-of-flight mass
spectrometry (LC-QTOF-MS/MS) system. All the variable parameters of the
DLLME method were optimized to improve the extraction output for all
analytes and the limits of detection and quantitation (LOD and LOQ)
values, which are quite satisfactory, were calculated under the optimum
conditions. Results: The LOD and LOQ values were found in the
range of 0.004 – 0.013 and 0.27 – 0.61 µg/L, respectively. The
detection limits achieved by direct LC-QTOF-MS/MS analysis were
increased by about 10 – 260 fold using the optimized DLLME method. To
assess the accuracy and applicability of the developed method, recovery
experiments on tropical fruits were carried out. The matrix-matched
calibration method was used to enhance the quantification accuracy of
the analytes in kiwi, pineapple, and mango matrices, with percent
recoveries ranging between 89 and 117%. Conclusion: The
results show that the proposed method is feasible for the determination
of pesticides with high accuracy and precision. The above approach acts
as a reference method for monitoring tropical fruits while proposing
prospective solutions for pesticides assessment in more complex
matrices.