Studies to Improve the Extraction Yields of Incurred Pesticide Residues from Crops Using the QuEChERS Method

Abstract

The influence of various factors on the extraction yields of incurred pesticides from crops using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method was thoroughly studied. These factors included extraction time, extraction temperature, agitation approach, and in the case of dry commodities, sample comminution grade. Extraction yields increased with increasing extraction time, eventually reaching a plateau. Extraction temperature also played an important role in speeding up extraction, whereas the agitation approach had little influence. Based on our results we propose an extension of the first QuEChERS extraction step to 15 min when using deep frozen samples and to 2 min when using samples at ambient temperature. The extension of the second QuEChERS extraction step was shown to be less effective. Mechanical shakers can be used to facilitate extraction. This minor modification of the QuEChERS method does not alter its simple structure nor increase the manual labor and costs involved. It was further shown that the extraction yields of incurred pesticides strongly depend on their physiochemical properties, with lipophilic pesticides typically showing stronger retardation and higher yields when extraction time and/or temperature are increased. The impact of prolonging the first QuEChERS extraction step from 1 to 15 min on the extraction yields of incurred pesticides from frozen samples was studied on 132 real samples containing 85 different pesticides throughout the polarity range and representing 55 different commodity types. Out of the 408 pesticide/commodity combinations studied, 34% showed >25% yield increases when the extraction time was extended to 15 min. Also, more than half of the 132 studied samples contained at least one incurred pesticide for which the extraction yield increased by more than 25%. Similar extraction retardation effects were also observed for spiked pesticides but only if these were spiked on commodities with intact surface, not to homogenates thereof.

Effects of milling on the extraction efficiency of incurred pesticides in cereals

“…Among the different analytical approaches developed so far, the QuEhERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method has become particularly important in this field due to its inherent advantages (Anastassiades et al 2003;Lehotay et al 2005;AOAC 2007;Sack et al 2011). Several factors may have an impact on pesticide extractability from cereals, such as the physicochemical properties of the pesticides, the accumulation of pesticides in the inner or cuticle parts of the grains, the time of pesticide application, and the crop type (Hepperle et al 2015). The incurred pesticide residues are not always easy to extract because they might be enclosed in cells, starch, or fat particles or may undergo strong interactions with the matrix.…”

“…To our knowledge, literature highlighting the effect of particle size on the extraction efficiency of pesticides in flour is very scarce. Recently, Hepperle et al (Hepperle et al 2015) studied milled and re-milled rice and wheat. However, except for chlorpyrifos in a wheat sample, they did not find higher extraction yields for other pesticides as a result of a higher comminution grade.…”

Non-targeted screening approaches for contaminants and adulterants in food using liquid chromatography hyphenated to high resolution mass spectrometry

“…These methods should be examined for use in non-targeted screening, and some research has begun in this area [33][34][35]. In particular, QuEChERS has been successively applied to different classes of compounds, including polar and non-polar compounds, with adequate recoveries [30,33,36,37]. Furthermore, QuEChERS has been successfully applied to diverse sample types including fruits and vegetables [38,39]; thus this sample preparation may be sufficient or easily modified for non-targeted screening.…”

Influences of sample homogenization time and standing time before extraction on the determination of incurred pesticide residue levels in grapes

“…[1][2][3][4][5][6] It is also necessary to prepare an adequate sample homogenate with fine particles to reduce the uncertainty induced by errors in weighing the extract portions analyzed and to ensure sufficient extraction efficiency for pesticide residues in the samples. [6][7][8][9][10] It is necessary to weigh extract portions from a sample homogenate without a bias in content between the peel and pulp portions of fruits, because the majority of pesticide residues from foliage ap-plication with short pre-harvest intervals are present in the peels of fruits such as melons. 11) Similarly, it is necessary to prepare a sample homogenate without a bias in content between the outer and inner leaves of wrapped leafy vegetables such as cabbage, because the majority of pesticide residues from foliage application are present in the outer leaves.…”