The objectives of the CORESTA Agrochemical Analysis Sub-Group are to perform regular proficiency testing of multi-residue methods for the analysis of Crop Protection Agents (CPA’s) in tobacco, to undertake joint experiments to resolve identified issues, and to work on Technical Guidelines and Technical Notes for method development and improvement. Annual studies include more than 20 participations from tobacco industry and independent commercial laboratories, authorities and universities. Information about these studies and the consequences deserve to get a wider recognition by the industry.

Results from Proficiency Tests (PTs) conducted since 2005 using the FAPAS testing scheme will be reviewed and then assessed.

Calculating the weighted average of squared z-scores for all studies over time will be used to assess long term laboratory performance (in general and per lab). Additionally, statistical evaluation of variability of analytical results will demonstrate the consequences of lab performance when comparing results to CORESTA’s Guidance Residue Levels (GRLs). The results indicate that continuous ring trials improve the quality of participating laboratories significantly over time. Big differences in improvement were found between regular and occasional participants. However, when calculating the weighted average of squared z-scores for all studies, a significant decrease is observed over years indicating overall significant progress in quality.

The best performing laboratories show average weighted squared Z-score above 2, where other laboratories can have scores above 5. The consequences of these values for the interpretation of results will be demonstrated. The variability of the sampling will be compared with the laboratory variability.

The joint experiments, scientific dialogue and exchange of available knowledge result in continuous innovation and more reliable analyses of CPAs. The quality of the laboratory in the PTs has an important impact on the evaluation of the samples in view of CORESTA GRLs.