Estudo comparativo das fontes de ionização esi e apci em sistema lc-ms/ms para validação de método multirresíduo de agrotóxico em hortaliças

Abstract

Pesticide contamination is a topic that has attracted attention, since uncontrolled use in the field can lead to the presence of residues of these compounds in food, which can represent a risk to human health. Pesticides are compounds used in agriculture in order to avoid damage caused by a variety of animal and plant species. Generally, the most sensitive techniques are used in the analysis of pesticides, such as gas and liquid chromatography coupled to mass spectrometry (GC-MS, LC-MS). Both techniques present high analytical performances, but requires laborious stages of sample preparation before instrumental analysis. Therefore, it is essential to develop analytical methods for determining pesticides residues in food. This work involves the development, optimization and validation of an analytical method for simultaneous determination of 17 pesticides in samples of vegetables sold in Fortaleza – Ceará using LC-MS/MS. The main objective is to compare the efficiency of two ionization sourcesat atmospheric pressure (API) in an LC-MS/MS system: Electrospray Ionization (ESI) and Atmospheric Pressure Chemical Ionization (APCI), evaluating the sensitivity and matrix effect of the compounds under study. The QuEChERS-Citrate method was used to prepare the matrix extract, pesticides-free, to construct the analytical curves by matrix-matched calibration. Figures of merit such as selectivity, Limit of Detection (LOD), Limit of Quantification (LOQ), linearity and accuracy were evaluated through the recovery tests of the method. The analytical curves were statistically validated, presenting a good linearity in both sources, with coefficients of determination above 0.99, according to the guidelines established by ANVISA and MAPA. Limit of Detection (LOD) values ranged from 0.05 to 0.25 µg L-1 and Limit of Quantification (LOQ) ranged from 0.1 to 1.0 µg L-1in ESI source; and ranged from 0.25 to 0.5 µg L-1 for LOQ, and 0.75 to 2.0 µg L-1 for LOD, in APCI source. Accuracy and precision were evaluated at three concentration levels (2, 10 and 50 μg kg-1). Most of the compounds presented good results in the recovery of the method, meeting the recommendations of the standards adopted for the present study. The ESI technique presented a better response in terms of sensitivity, showing lower detection limits. The results of the matrix effect study demonstrated that the APCI source has advantages for most of the pesticides investigated. Thus, the method was applied to 15 samples divided among the matrices under study in the present work. Among the samples analyzed, acephate was found in 7 (3 samples of cabbage and 4 samples of broccoli. Chlorpyrifos was also found in a cabbage sample, although it has no authorized use for this crop, as well as the pesticides dimethoate, malathion, profenofos and propiconazole, but these were below the limits of quantification of the method.