AOAC SPIFAN Nutrients ERP (December 7, 2022)

For ERP/Working Group Use Only DO NOT DISTRIBUTE Fluor-04 (SLV) Resubmission FOR ERP USE ONLY DO NOT DISTRIBUTE

Accuracy The five SPIFAN matrices were spiked with three amounts of an NIST-traceable fluoride standard solution (Thermo Scientific Orion 100 ppm fluoride standard, part number 940907, lot AU1: 99.8 ± 0.5 ppm) and analyzed per the method. The spike levels were chosen to span the analytical range specified in the SMPR (30-200 µg fluoride/100 g reconstituted product). This was repeated six days. Water blanks were also spiked and analyzed using a similar procedure. Linearity During each run, a series of ten fluoride standards were prepared using an NIST-traceable solution (Orion 100 ppm fluoride) with concentrations ranging from 2 to 200 µg/100 g (0.02 – 2 ppm). Two calibration curves (5 standards each) were calculated using a least squares (log fit) analysis of the electrode response versus standard concentration. LOD/LOQ The detection limit of the fluoride electrodes is given by the manufacturers as 0.02 ppm (2 µg/100 g), which is well below the SMPR requirement of 30 µg/100 g. The method LOQ can then be calculated based on the maximum weight used for each sample. Based on a typical sample weight of 50g, the LOQ is estimated to be 4 µg/100 g in prepared sample. Ruggedness Method ruggedness was demonstrated by using a total of two independent electrode configurations from two different vendors. Calibration standards were prepared daily, and the citrate buffer was prepared several times throughout the validation as needed. Specificity It has been reported that the only interference to the fluoride electrode is hydroxide ion when the level of hydroxide is greater than one-tenth the level of the fluoride ion present. In neutral samples (pH > 5.0) this interference is negligible. (Electrode User’s Manual, Orion.) Acceptance Criteria The standard method performance requirements (SMPR 2014.016) are summarized as follows:

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