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

PAGE SIX – SELECTIVITY STUDY - INTERFERENCE

Interference The matrices identified in Annex A, Table 2 will be spiked with gluten from each claimed gluten source at three times the LOQ of the method (as long as that is equal to or below 20 mg/kg, otherwise test at 20 mg/kg). Test material preparation is described in Annex B. One test portion of each spiked test material will be analyzed with the candidate method as it is designed for testing food products. If a result is obtained that is above the measurement range of the method, the extract must be diluted and rerun to obtain the exact amount of analyte. The absorbance or optical density (OD) values for all test portion extracts and standards must be reported. The extrapolated concentration for all test portions that had an absorbance or OD above the limit of quantitation of the method must be reported. If any analysis is repeated, both datasets must be reported and a justification given for all repeat analysis. The percent recovery should be calculated and reported for each tested food. Spiked test materials must render a result above the LOQ. In the event that the single test portion replicate tests below the LOQ, that food matrix may be retested in 6 additional test portions, with no results below the LOQ allowed, to rule out interference.

Delete "extrapolated", since extrapolation is not necessary for results above the LOQ.