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

3. Quantitation limit The detection limit for the fluoride specific ion electrode is 0.02 ppm. If the measured concentration of the diluted sample is less than 0.02 ppm, and the maximum sample weight has been used, then the fluoride concentration must be reported as less than the calculated quantitation limit for that sample weight. The calculation is as follows: ∗ − =< ℎ ℎ ℎ Where: DL = Quantitation limit of electrodes (0.02ppm) X = Tare weight for beaker Y = Sample weight Z = Weight of beaker, sample, and dilution agents (acid, buffer) Example: The maximum sample weight of an Infant Formula Milk Based RTF is used and the sample concentration from the calibration curve is predicted to be 0.016 ppm. This is less than the quantitation limit for the method and the result is reported using the calculation above.

X = 3.2669g Y = 48.3570g Z = 113.8393g QL = 0.02ppm

113.8393

3.2669

g

g

0.02

0.048

Fluoride ppm

×

= 〈

ppm

48.3570

g

G. MISCELLANEOUS Note: The following information is useful when troubleshooting instrument problems and is not performed on a routine basis. 1. Fluoride electrode best practices: a) Maintain filling solution level of ~ 1 cm below opening by adding fresh filling solution as needed b) Filling solution level must be at least 1 inch above the sample level for proper flow c) Flush and refill electrode when excessive crystallization of filling solution occurs

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