Results of the 16th proficiency test on the determination of pesticide residues in olive oil

Abstract

The Italian National Reference Laboratory (NRL) for pesticide residues yearly organizes proficiency tests (PTs) on olive oil in cooperation with the International Olive Council, addressed to European laboratories (NRLs, official control laboratories, and private laboratories), involved in the National and European monitoring programs. The main aim of these PTs is to compare the performances of the laboratories in Mediterranean and European countries and to promote mutual acceptance of pesticide residue data regarding the analytical controls of olive oil. In this paper, a description of the last PT named COIPT-16 is presented. The test material consisted of a commercial olive oil spiked with six different pesticides. The assigned value of each analyte was determined as a consensus value based on the results of the participants calculated using Algorithm A of the ISO 13528:2015. As relative target standard deviation in the z score formula, the 25 % of the robust mean value was considered. The global performance of each participating laboratory was assessed by calculating the average of the squared z scores only for laboratories that have detected at least 80 % of the analytes present in sample achieving the sufficient scope as indicated in the initial protocol. Two compounds, alpha-endosulfan and beta-endosulfan have been analyzed again in this PTas in the previous PT to compare the performances of the laboratories whose supplied results both PTs. The quick, easy, cheap, effective, rugged, and safe methodology was used by the majority of laboratories corresponding to 64 % of participants.