Studies on the Extractability of Incurred Pesticides
The EURL-SRM, in collaboration with the EURL-FV and the EURL-CF, has investigated the extractability of pesticides from fruits and vegetables and cereals respectively.
An overview of the results of this study is given in the following presentation: DOWNLOAD HERE (pdf-file)
SUMMARY:
The impact of different extraction conditions, such as extraction solvent, temperature and agitation approach, on the extraction yields of incurred pesticides from various commodities (real samples as well as EUPT-samples containing incurred and post-harvest spiked pesticides) was studied.
The main focus of this ongoing study has been on QuEChERS, where acetonitrile is em-ployed for extraction, but the QuPPe method involving methanol as well as acetone- and ethyl acetate-based methods were also studied.
Extractions of frozen material showed extraction yields of incurred pesticides reaching a "pla-teau" typically after ca.10-15 min extraction. Extractions at room temperature were consid-erably faster (plateau at ca. 2 min) but processing of frozen samples is still recommended because of the better stability of pesticides when samples are stored frozen and considering that the time frozen samples require to reach room temperature is much longer (>60 min). The use of mechanical shakers is recommended. The agitation intensity seems to play a less significant role in the extraction yields.
More than 120 different real samples containing more than 70 different pesticides and me-tabolites were studied to observe the differences in the extraction yields of pesticides from frozen homogenates when comparing 1 min shaking by hand (typical QuEChERS conditions) versus 15 min using mechanical shakers. Pesticide lipophilicity was shown to be the factor influencing the extraction yields the most. Setting the yield at the "plateau" (15 min mechanical shaking) at 100 %, pesticides having logP>4 (less polar) showed average yields of ca. 75 % when extracting 1 min by hand, whereas pesticides with logP<2 (more polar) showed yields of ca. 95 % on average. No clear trend could be observed as regards the sample types. Approximately half of the samples tested contained at least one pesticide showing a yield < 75 % when extracting 1 min by hand, compared to 15 mechanical shaking.
The impact of particle size was also studied in the case of dry commodities and was shown to be significant.
Your EURL-SRM-Team
Published 30-11-2011, 12:13:40
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