Assessment of the performance of nine Greek laboratories through a proficiency test on the analysis of grapes for the determination of residues of pesticides

Abstract

A test material of grape homogenate spiked with 10 pesticides at concentrations 0.005–1.25 mg/kg was distributed to 11 Greek laboratories for analysis. The test material was checked by the organizer for homogeneity and stability and found homogeneous and stable. Ten laboratories reported results, one of them considered to be an independent laboratory. The assigned value for each analyte was the spiking concentration and the target standard deviation was evaluated from the Horwitz equation. Out of 36 z-score values 31 were acceptable, 4 questionable and 1 unacceptable. The overall performance of the laboratories was also estimated, one laboratory failing to the sum of squared z-test.

Keywords:

• Pesticides
• Grapes
• Proficiency test