Evaluation of the reproducibility standard deviation in the pesticide multi-residue methods on olive oil from past proficiency tests

The data reported in the frame of proficiency testing (PT) exercises organized from 2007 to 2016 have been statistically re-evaluated using Algorithm A of the ISO 13528:2015, and the relative standard deviation for reproducibility of multi-residue methods for the determination of pesticides in olive oil was evaluated. Usually, the assigned between-laboratories variability in PTs on pesticide residues is fixed/set to 25 %. This value was compared to the calculated robust relative standard deviation (RRSD). A total of 1527 analytical results were collected in the ten PTs for the determination of pesticides in olive oil. An RRSD of 21 % was obtained, below the maximum value of 25 %. If all participants use the same analytical approach (e.g., multi-residue method and same instrumental technique), a lower value of the reproducibility standard deviation should be expecting. The QuEChERS method, coupled with LC–MS/MS and GC–MS/MS, has become an important methodology for the analysis of pesticide residues. This is due to its simplicity, the use of low quantities of acetonitrile, the possibility to analyze a large number of pesticides with fewer steps and high efficiency. This method may harmonize the future of pesticide residue analyses. Recently, it was successfully applied to the analysis of olive oil by 70 % of the laboratories participating to our last PT exercise. An expanded uncertainty of 50 % was systematically applied in Europe since 2006 for the analyses of pesticides; the use of the QuEChERS methodology may reduce to 40 %. This work could contribute to promote the comparability of measurements of pesticide residues in foodstuffs.