Preparation and application of proficiency testing sample of myclobutanil and procymidone in apple powder

Objective To prepare pesticide residues in fruit matrix samples that meet the requirements of homogeneity and stability for the proficiency test.

Methods The pollution-free apple was selected as the main raw material to prepare the pesticide residue proficiency test samples of myclobutanil and procymidone， and to evaluate the homogeneity and stability. The results of the proficiency test were assessed using robust analysis and Ζ value.

Results The homogeneity and stability of the reference materials met the relevant requirements. Among 109 laboratories participated in the proficiency testing， 107 （98.2%） laboratories had satisfactory results. Suspicious test results were reported only in two laboratories， one laboratory for each of the two assessment items.

Conclusion An apple powder matrix sample with pesticide residues is successfully prepared for proficiency test， and could provide an evaluation tool for pesticide residue testing laboratories.