Preparation and Application of Proficiency Testing Sample for Pesticide Residues in Spinach Powder
Establish a method for the preparation of proficiency testing samples of thiamethoxam and clothianidin in lyophilized spinach powder.Blank spinach was used as the substrate,different concentrations of thiamethoxam and clothianidin standard solutions were added,and the proficiency testing samples in lyophilized spinach powder were prepared by freeze-drying.The uniformity and stability of samples were assessed according to the CNAS-GL003:2018 Guidelines for the Evaluation of Uniformity and Stability of Samples for Capability Verification.The proficiency testing of thiamethoxam and clothianidin in spinach powder was organized and implemented.The Z ratio score was used as the statistic to evaluate the test results of the participating laboratories.The F-test method was used to evaluate the homogeneity experiment,and the F value of the sample uniformity experiment was 1.03-1.60,which was lower than the table value F0.05(9,10)=3.02.The t test method was used in the stability experiment,and the t value of the sample stability experiment was 0.12-1.72,which was also lower than the table value t0.05(24)=2.064.The results showed that the uniformity of thiamethoxam and clothianidin in the prepared spinach freeze-dried powder could meet the requirements,and the contents of thiamethoxam and clothianidin were stable under room temperature storage conditions,which could be used for quality control in personnel assessment and proficiency testing in laboratories.
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