Measurement Uncertainty Associated with Sample Processing of Oranges and Tomatoes for Pesticide Residue Analysis

Abstract

The homogeneity of analytical samples and the stability of pesticides during the sample processing of oranges and tomatoes were evaluated. The mean concentrations of 14C-labeled chlorpyrifos in analytical portions (subsamples) after processing show that homogeneity is dependent on sample type as well as the processing procedure. The homogeneity of analytical samples of tomatoes processed cryogenically was much better than those processed at ambient temperature. For tomatoes, the minimum analytical portion masses required for between-analytical portion variation of < 0.3 Ho were 110 and 5 g for processing at ambient and cryogenic temperatures, respectively. Results for orange showed that analytical portion sizes of 5 g provided sufficient homogeneity from both sample processing procedures. Assessments of pesticide stability demonstrated that most were relatively stable during processing at either ambient or cryogenic temperatures. However, some pesticides, including dichlofluanid, chlorothalonil, tolylfluanid, and dicloran, appeared to suffer much greater losses (>20%) during processing at ambient temperature. For these analytes, loss is interpreted as chemical degradation.

Use of an Efficient Measurement Uncertainty Approach To Compare Room Temperature and Cryogenic Sample Processing in the Analysis of Chemical Contaminants in Foods

“…The only other spiked analytes observed to yield <85% recoveries were methamidophos, dichlorvos, and chlorothalonil. The former two pesticides are the most volatile analytes, and the third is known to degrade . As also reported in previous comparisons of cryogenic versus room temperature sample processing conditions, − Table indicates small losses of the volatile dichlorvos (14% relative difference) and unstable chlorothalonil (21%) during comminution at room temperature.…”

“…This bulk sample is then comminuted to generate a representative test sample portion, typically 10–50 g, for analysis. , As a result of resource limitations and sample throughput needs, sample processing in most routine laboratories is conducted at room temperature. However, it has been demonstrated that cryogenic processing using dry ice (solid CO 2 ) or liquid nitrogen often produces more reliable results. − For chlorpyrifos in tomato using a specific chopper, Fussell et al. showed that the same degree of analyte variability could be achieved for a 5 g test sample when using dry ice as 110 g at room temperature, whereas for orange, a subsample size of 5 g provided sufficient homogeneity for both sample processing procedures .…”

“…However, it has been demonstrated that cryogenic processing using dry ice (solid CO 2 ) or liquid nitrogen often produces more reliable results. − For chlorpyrifos in tomato using a specific chopper, Fussell et al. showed that the same degree of analyte variability could be achieved for a 5 g test sample when using dry ice as 110 g at room temperature, whereas for orange, a subsample size of 5 g provided sufficient homogeneity for both sample processing procedures . Another study showed that, in the case of fish filets, 2 g subsamples were sufficiently representative when using cryogenic conditions …”

Guidelines for the validation of qualitative multi‐residue methods used to detect pesticides in food

“…It is recommended that all laboratories should check that the sample processing procedures employed are fit‐for‐purpose. Secondly, and particularly for fruit and vegetable samples, homogenization at room temperature will disrupt plant cells and release enzymes that can rapidly react and/or degrade certain pesticides . Cryogenic sample processing can reduce both heterogeneity and improve pesticide stability and is therefore recommended for such samples.…”

Testing a cumulative and aggregate exposure model using biomonitoring studies and dietary records for Italian vineyard spray operators

“…Each duplicate food sample was stored by the volunteers using a fridge box previously provided. At the end of the test days, the samples were transported to the laboratory and immediately homogenised in the presence of dry ice (Fussell et al, 2007).…”