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Accuracy
Accuracy was determined by fortifying the placebo samples (prior to sample preparation)
at 50 and 100 % of the typical level of fluoride and chloride found in a powdered infant formula.
These recovery experiments were performed over multiple days. In addition, NIST SRM 1849a
was analyzed during the course of this validation. Table 2 & 3 contains recovery results for
fluoride and chloride on the five placebo samples respectively.
The percent fluoride recovered ranged from a low of 80.7% to a high of 105%. The
percent relative standard deviations (RSD) ranged from a low of 1.30% to a high of 4.45%. The
overall mean recovery is 93.9% (RSD of 2.39%) for 50% spiked level and 91.9% (RSD 3.04%)
for 100% spiked level. All data meets the criteria specified in the SMPR (80-120% recovery).
The percent chloride recovered ranged from a low of 94.7% to a high of 106%. The
percent relative standard deviations (RSD) ranged from a low of 0.46% to a high of 3.33%. The
overall mean recovery is 100% (RSD of 1.53%) for 50% spiked level and 101% (RSD 1.62%)
for 100% spiked level. With the exception of two data points 94.7% and 106%, all data meets the
criteria specified in the SMPR (95-105% recovery).
Results on NIST SRM 1849a can be found in Table 4. The mean value (n=12) of fluoride
and chloride were found to be 195 μg/100g (RSD of 2.74%) and 7454 mg/Kg (RSD of 1.90%).
The certified value for Chloride is 7010 mg/Kg whereas the certified value and range for fluoride
are not provided in the SMPR.
Precision
Repeatability was evaluated on all 13 fortified AOAC SLV test material matrices
including the NIST SRM 1849a. Samples and standards were prepared fresh in twice every day
over six days and analyzed to calculate the intermediate (n=2) and overall reproducibility (n=12).
Precision data for all samples can be found in Tables 5, 6 and 7.
Fluoride concentration ranged from 16.8 to 668 μg/100 g. Overall precision was < 10%
for all samples. Percent relative standard deviations ranged from a low of 1.38% to a high of 9.35
%. Chloride concentration ranged from 356 to 814 mg/100 g. Overall precision was < 3.5% for
all samples. Percent relative standard deviations ranged from a low of 1.22% to a high of 3.16 %.
Reproducibility
Reproducibility was determined in the precision experiments conducted over multiple
days and involving different lots of reagents made fresh each analysis day.
Limit of Detection (LOD) and Limit of Quantitation (LOQ)
The LOD was estimated as 3× the signal-to-noise ratio (S/N) and the LOQ as 10× the
S/N. The system baseline noise for the LOD and LOQ was determined by measuring peak-to-
Fluor-02/Chlor-03 (February 2016)
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