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

curve data in Tables III and IV ). The expected slope for calibration curves generated by graphing the log of the fluoride concentrations against the mV reading typically range from 54 – 60 mV per 10-fold change in concentration. The average slope for the high curve was -55.7 and -55.9 for the two electrodes. The slope for the low curve fell outside the typical range, with averages of -40.8 and -40.9. This is not unexpected, as the calibration deviates from linear near the detection limit. Figure 3 shows an example of the calibration curves used in this SLV, illustrating the deviation from linear in the lower standard range. (Note: high and low standards are all plotted on a single curve per electrode).

Fluoride Standard Curves

100.0 120.0 140.0 160.0 180.0 200.0

0.0 20.0 40.0 60.0 80.0

Electrode Potential, mV

-2.000000

-1.500000

-1.000000

-0.500000

0.000000

0.500000

mV Reading, Electrode #1 mV Reading, Electrode #2

Log Concentration

Figure 3: Calibration curve example

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