Matrix effects observed during pesticides residue analysis in fruits by GC

Abstract

The influence of the sample matrix in the GC-electron-capture detection analysis of the pesticides dimethoate, diazinon, chlorothalonil, parathion methyl and fenitrothion in fruits samples has been studied. Experiments have been carried out where the pesticide responses in standard solutions prepared in selected solvent were compared with their response when present in apple, mango, papaya, banana, pineapple and melon extracts. The presence of matrix effects (MEs) and their extent were shown to be simultaneously influenced by several factors (matrix concentration, matrix type, pesticide concentration, analytical range). Pronounced MEs were observed particularly for dimethoate and diazinon in all matrices tested; in lower concentrations, all pesticides presented significant ME. The other pesticides presented variable ME. Higher ME enhancement was detected at lower pesticide concentration levels of and/or at higher matrix concentration solutions. The ME detected for fenitrothion, in the analytical range evaluated, were dependent on matrix type. For each pesticide, solvent and matrix-matched calibrations were compared for all fruit samples, and it could be concluded that quantitation based on standard solutions prepared in blank matrix extract (matrix-matched calibration) should be used to compensate the MEs and to obtain more accurate results for the pesticides studied. IntroductionMost of the pesticide determination in food samples is usually performed using GC in combination with electroncapture detection (ECD) [1,2], nitrogen-phosphorus detection [2,3] or MS detection [4][5][6].Analytical procedures for determination of pesticides in fruit matrices are usually based on an extraction step, using conventional liquid-liquid extraction, followed by a clean-up procedure prior to chromatographic analysis [7,8]. Several methods based on supercritical fluid extraction [9, 10], solidphase extraction [11,12], solid-phase microextraction [13], stir bar sorptive extraction [14][15][16] and matrix solid-phase dispersion (MSPD) [1,5,[17][18][19][20][21][22][23] have been developed to overcome the drawbacks caused by using high amounts of glassware and toxic solvents in the classical liquid extraction methods.MSPD has proven useful as an extraction technique for the determination of pesticide residues in fruits and vegetables by GC [1,4] or LC [18,19]. The MSPD procedure allows the extraction and cleanup of analytes in a single step and is based on the dispersion of the sample on an adsorbent, such as florisil, C18, alumina or silica, followed by eluting with a small amount of solvent [24]. However, in spite of the fact that most of these modern methods provide a simple and rapid procedure for the determination of pesticides in fruits matrices, they do not avoid the presence of co-extracted matrix components that can result in a matrix effect (ME) in the pesticide analysis [25][26][27].MEs are notoriously variable in occurrence and intensity, the GC technique being particularly prone to them [5,28]. The ME is a phenomenon th...

The apple-matrix effect on GC/MS response of cyprodinil, pyrimethanil and trifloxystrobin standards

“…Since the matrix effect changes from one sample to another, i.e. depends on the matrix type, some authors have suggested the application of the matrixmatched calibration method [11], which is considered as one of the most practical solutions. When no blank matrix is available for the matrix-matched calibration procedure, a standard-addition method is performed [17].…”

“…Matrix effect -dilution trendline is similar for all pesticides. Another study, dealing with the response of several pesticides in the apple matrix, demonstrated the dependence of the matrix effect on the matrix concentration -a gradual increase in response of dimethoate, chlorothalonil and fenitrothion was observed, as the matrix concentration in the solutions increased from 0.1 to 1.0 g mL -1 [11]. The study furthermore revealed that besides matrix concentration, the matrix effect depends on the matrix type, pesticide concentration and analytical range.…”

Insecticides extraction from banana leaves using a modified QuEChERS method

“…One of the most used methods to compensate them is the development of a matrix matched calibration (De Sousa Freitas & Lanças, 2009;Zrostlíková, Hajšlová, Poustka, & Begany, 2002), which was also carried out in this work. For this purpose, comparison of the slopes and intercepts of the calibration curves of pure standards dissolved in cyclohexane and of pure standards dissolved in the final sample extract (which is also cyclohexane) was developed.…”

Evaluation of the matrix-like effect in multiresidue pesticide analysis by gas chromatography with tandem mass spectrometry

“…In addition, it has been briefly noted in EU analytical guideline SANTE/11945/2015 that the detector response of individual pesticides in multipesticide calibration standards may be affected by one or more of the other pesticides in the same solution (http://ec.europa.eu/food/plant/docs/plant_pest-icides_mrl_guidelines_wrkdoc_11945_en.pdf"). However, this unnamed phenomenon has been rarely studied compared to the "matrix effect" in GC analysis, which has been studied widely [1][2][3][4]6,13,15,19,21,[25][26][27]. To the best of our knowledge, the response-altering phenomenon resulting from several coexisting pesticides has not been demonstrated in the scientific literature.…”