Results from Rounds 0 to 2 from the Interlaboratory Proficiency Program for Analysis of Pesticides on Raw Wool

Abstract

The participating laboratories in the Wool Residue Interlaboratory Proficiency Program have returned results for Round 2, the second assessable round conducted in the current program. The results of the first assessable round, Round 1, were reported to the Raw Wool Group at the Biella meeting of IWTO in November 2005.

There was discussion that the results from the first assessable round appeared slightly poorer than for the Round 0 familiarisation round. This report presents the results from the individual laboratories that participated in Round 0 and compares them with the results from Round 1. The familiarisation round had five participating laboratories, three of which participated in the original interlaboratory proficiency program, and were considered to have significant experience in the analysis of pesticides in a wool wax matrix. The other two were relatively inexperienced in the area of multi-residue chemical analysis testing. The results of Round 0 showed 2 false negatives, 2 false positives and 13 outliers, while the Round 1 results showed 22 false negatives, 13 false positives and 23 outliers from the six participating laboratories.

Two of the more experienced laboratories that participated in Round 0 did not enrol in Round 1, while three new laboratories, two of whom were less experienced, joined the program. The results from Round 1 reflect the fact that the majority of the participating laboratories had less experience in dealing with the difficult wool matrix. In addition the average spike concentrations in Round 1 samples were closer to Limit of Reporting (LoR) concentrations than those in the Round 0 familiarisation round, and this added to the difficulty.

The outcomes from Round 2 are anticipated to improve over the Round 1 results, as laboratories have had the opportunity to refine and modify their methods and procedures in the light of the feedback provided on expected results of the preceding round. In addition, the laboratories have all been sent a selection of papers from the chemical literature, but they may not yet have had a chance to implement revised procedures.

An accompanying paper (RWG 04) provides details of a simple and robust analysis procedure that was previously used by CSIRO to achieve satisfactory results in the original proficiency program. It does not rely on sophisticated processing or extraction equipment and should be able to be implemented by most laboratories if  needed. It should allow laboratories to develop a stable base method that they can then adapt and optimize to suit their needs.

The results from Round 2 were not available at the time of this report, but will be added as an appendix to the IWTO Raw Wool Group meeting at Cairo in May 2006. 

Citation

"Results from Rounds 0 to 2 from the Interlaboratory Proficiency Program for Analysis of Pesticides on Raw Wool", W. Korth, S. Maddalena, I.M. Russell, Report 05, Raw Wool Group, IWTO, Cairo Meeting, May 2006.