AOAC GFA Stakeholder Program Meeting Book (August 27, 2023)

PAGE ELEVEN – COLLABORATIVE STUDY – TEST MATERIALS

6.4 Test Materials: Appendix D requires a minimum of 5 materials be used in the collaborative study. (11) Three materials are allowed but only when a single specification is involved for a single matrix. For the purposes of this requirement, a material is defined as a combination of the test component, matrix, and concentration to which the method performance parameters apply. Two blind-coded replicate test portions should be analyzed by each laboratory for each test material (i.e., each matrix-concentration combination). For each matrix, the concentration levels must include a blank (zero) and a level at less than or equal to two times the LOQ stated in the kit insert (as long as this is less than or equal to 20 mg/kg, otherwise test at 20 mg/kg). The remaining concentrations should be distributed throughout the quantification range. (7) Incurred test materials are required for estimation of precision, sensitivity, and recovery. See Annex B for description of best practices for incurred matrix preparation.

As regards the use of a minimum of 5 materials and for the sake of clarification, could an example be provided?