AOAC SPIFAN Nutrients ERP Review (March 14, 2019)

Fluor-03 (Feb. 2019) FOR ERP USE ONLY DO NOT DISTRIBUTE

Figure 6 Example for the low (upper figure) and high (lower figure) level calibration for fluoride. The best calibration fit for anions can be reached with a quadratic function. For the low calibration the intercept was set to zero, as interferences from impurities and contaminations through sample preparation are not expected for fluoride. (b) Sample concentration. —Determine the peak height for fluoride in each sample (see Figure 7 for a chromatogram for the reference material SRM 1849a); set a horizontal baseline similar to the standards. Calculate the concentration of fluoride in the sample (c(F - ) S ) using the quadratic calibration function (low/high level depending on sample concentration). Calculate the sample fluoride concentration for the final product (c(F - ) FIN ) as following: ( − ) = 100 × ( − ) × 1000 × c(F - ) FIN = Calculated concentration for final product (µg/100 g) c(F - ) S = Calculated concentration from calibration curve (µg/kg) W S (g) = Sample weight (g) (see chapter F) W UPW (g) = UPW weight (see chapter F)

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