Proficiency Testing for the HPLC Analysis of Azoxystrobin, Imidacloprid and Methabenzthiazuron Residues in Soil

The proficiency testing for the residue laboratories of pesticide registration was conducted inorder to improve the reliability and the ability for pesticide residue analysis. On November 2012 the testingwas carried out using the soil collected and kept as the moistened state for five years, which was expected tovery low residue levels of pesticides. The soil was fortified with azoxystrobin, imidacloprid and methabenz-thiazuron in a manner similar to prepare soil samples for indoor soil degradation test, and then sub-sampleswere prepared for the distribution to participants. Some of them were randomly selected for confirm ofhomogeneity and to ensure the stability of samples at room temperature. Samples were consisted of two soilstreated as different levels, one of which was used to the assessment and another used to confirm. In addition,provided three standard solutions, respectively concentration of 10 mg/L, and untreated soil. Forty eightinstitutions submitted results. The medians of results were used as the assigned values for pesticide residues.Fitness for purpose standard deviation of proficiency test was calculated by applying 20% RSD as thecoefficient of variation allowed in the soil residue test. Z-score was applied for evaluation of individualpesticides, and the average of the absolute value of the Z-score for the overall assessment of pesticides.Laboratories evaluated the absolute value of the Z-score less than 2 to fit the case of azoxystrobin were 48,imidacloprid and methabenzthiazuron 46.Key words pesticide, residue analysis, quality assurance, proficiency test