AOAC SPIFAN Nutrients ERP (December 7, 2022)

Fluor-06 (SLV) 10-2022 FOR ERP USE ONLY DO NOT DISTRIBUTE

The recoveries were also determined from duplicate analysis of spiked reference materials. The results are shown in Table 8. In all cases the recovery is within the required limit.

Table 8. Recoveries(%) in spiked SRM samples (averages of two determinations). SRM1869 (+ LOW spike) SRM1849a (+ MED spike) NIST10175 (+ LOW spike)

RM8260 (+ LOW spike)

RM8261 (+ MED spike)

Concentration (mg/kg)

1.3

1.5

0.3

0.2

0.9

Recovery (%)

93.5

93.0

98.7

100.3

94.7

RSD (%)

0.1

0.6

0.3

1.1

1.1

Slurries Several slurries were prepared and used during this single lab validation study, as mentioned in Table 2. For the slurries 25 g and was dissolved in 200 mL water. The recoveries for the slurries are listed in Table 9. Table 9. Recoveries(%) of QC samples (LOQ, Low, Med, High)). Sample Slurry F⁻ (mg/kg) QC-LOQ slurry 91.0% QC-LOQ slurry 97.8% QC-Low slurry 97.7% QC-Low slurry 96.3% QC-Med slurry 96.2% QC-Med slurry 88.7% QC-High slurry 96.8% QC-High slurry 97.0% The results found using direct solid sampling corresponds with the findings using slurry sampling. As the average value found for the QC-no spike slurry sample (NUT2022-1414) was 0.458 mg/kg, whereas the result found using direct solid sampling was 0.443 mg/kg. 5.5 Accuracy Since no reference material with a certified concentration is commercially or otherwise available, the accuracy cannot be established as such. Perhaps a comparison of the values determined in the SRM samples with other methods (e.g. Willard-Winter 7 , NMR 8 ) could provide an insight, but this is outside the scope of this study. 5.6 Repeatability For determination of the repeatability five different unspiked samples containing fluoride at levels of 0.2–1.5 mg/kg were analysed in 6-fold on one day by one technician on the same instrument. The results are shown in Table 10. The relative standard deviation (RSD) is ≤ 8% for all samples. The repeatability was also determined using QC samples spiked at four different levels. These results are included in the table showing the recovery data (Table 7).