Estimation and correction of matrix effects in gas chromatographic pesticide multiresidue analytical methods with a nitrogen–phosphorus detector

Abstract

The assessment of matrix effects in the quantification of organophosphorus pesticides in fruit and vegetables by GC-NPD, were studied applying ANCOVA. Calibration curves prepared in solvent were compared with calibration curves prepared in a blank matrix extract for eight different commodities, establishing whether the matrix induces systematic or proportional errors in the quantification of the pesticides. In such cases correction functions were obtained and validated by quantifying spiked samples using solvent calibrations and applying the correction functions to the data obtained. The results were compared with those obtained by quantification using matrix-matching calibrations and with those from 100% recovery experiments. It was found that the matrix effects can be avoided using the correction functions. Finally the contribution of the correction functions to the uncertainty of the results was estimated as well as their stability during a four month period.

Efeito de matriz na quantificação de agrotóxicos por cromatografia gasosa

“…[79][80][81][82] Na Figura 6A, B e C estão representadas as curvas analíticas de análises cromatográficas de deltametrina em tomate, 77 thiametoxan em solo e batata. 83 Em cada gráfico, as curvas analíticas dos agrotóxicos foram obtidas em solventes puros e em extratos das matrizes.…”

Rapid pesticide analysis, in post-harvest plants used as animal feed, by low-pressure gas chromatography?tandem mass spectrometry

“…Matrix effects have been described in the literature in the determination of pesticide residues in different fields by several authors [16,17,18,19,20]. Calibration curves were produced by using both matrix-matched (in each matrix) and solvent based standards of the same concentration, because the target vegetable matrices contain many compounds that are co-extracted in the extraction organic solvent.…”

Factors Affecting the Accurate Quantification of Pesticide Residues in Non-Fatty Matrices

“…Moreover, many non-fatty matrices are identified as tending to give matrix effects, such as apple, tomato, banana, orange peel, stone fruits, carrot, leafy vegetables, wheat, wine etc. (Miyahara et al, 1994;Egea González et al, 2002;Navarro et al, 2002;Patel et al, 2004;Georgakopoulos et al, 2007;Freitas & Lanças, 2009), due to the high co-extracts amount persisting in the GC analytical sample, necessitating the application of clean-up step(s) (Dorea et al, 1996;Hajšlová et al, 1998;Schenck & Lehotay, 2000;Li et al, 2008). It should also be addressed that matrix effects are difficult to study because of the different analysis conditions for the samples, since the effects of simple maintenance application (e.g.…”

“…Its use may result in several benefits, such as elimination of matrix interferences causing such phenomena, high recoveries, detection and quantification limits (LODs and LOQs, respectively), reduction of maintenance needs for the GC instrument due to the relatively clean extract (e.g., lower changes of liners and capillary columns, smaller detector contamination by the impurities) and restriction of enhancement effects (Hajšlová et al, 1998;Schenck & Lehotay, 2000;García-Reyes et al, 2007). The major disadvantage is the demanding for extra labor time and cost (Greve, 1988;Egea González et al, 2002;Beyer & Biziuk, 2008;Schenck & Wong, 2008) because of the increasing needs for additional solvent amounts, columns (Florisil, SPE) and sorbents (primary secondary amine-PSA, octadecyl-C 18 , graphitized carbon black-GCB) (Dorea et al, 1996;Schenk et al, 2002;Anastassiades et al, 2003a;Li et al, 2008). It should also be noticed that the more the steps of an MRM, the higher the possibility for analytes partial loss and the increase of the combined uncertainty during the procedure (Hajšlová et al, 1998;Menkissoglu-Spiroudi & Fotopoulou, 2004;Poole, 2007).…”

“…These standards are prepared by adding appropriate aliquots from solvent standard solutions in blank matrix extracts (Erney et al, 1997;Štajnbaher & Zupančič-Kralj, 2003;Lesueur et al, 2008;Freitas & Lanças, 2009;Georgakopoulos et al, 2009). Their application has nowadays been included in the calibration step for pesticides quantification (Erney et al, 1993;Bernal et al, 1997;Egea González et al, 2002;Martínez Vidal et al, 2004). For calibration by comparing the quantity of a fortified extract with the respective of a matrix-matched standard, the concentration of the standard should be equal to the final concentration of the extract; otherwise the result is incorrect (Erney et al, 1997;Georgakopoulos et al, 2009).…”