AOAC SPIFAN Nutrients ERP Method Reviews (September 7, 2019)

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were still below its quantification limit; of the 10 remaining samples, 8 fell below the SMPR analytical range.

The results for all samples that were successfully quantified were used in the SLV summary data.

Method Optimization:

• Performance Characteristics:

Analytical Range: SMPR: Range: 30 – 200 mcg/100g reconstituted powder

LOQ: SMPR: 30 mcg/100g reconstituted powder  Method PLOQ estimated at 4 mcg/100g reconstituted powder based on lowest standard concentration in standard curve (0.02ppm) and typical sample dilutions.

Accuracy/Recovery: SMPR Requirements:

 30 – 100 mcg/100g reconstituted powder: 80 – 120%  > 100 mcg/100g reconstituted powder: 90 – 110%

Spiking was performed on 7 sample matrices, 1 of which was below the PLOQ, 4 of which were below the SMPR analytical range, and 2 of which were in the lower analytical range. Spiking was performed at 2 different levels (corresponding to the SMPR ranges), was repeated three or more times, was performed by different analysts, and the assays performed using different electrode configurations. Recovery results were reported as a grand mean for each sample (rather than results by spike level) and fell within the range of 93.5 – 109.9%, meeting the SMPR requirements.

Precision (RSD r ): Requirements:

 30 – 100 mcg/100g reconstituted powder: ≤ 8%  > 100 mcg/100g reconstituted powder: ≤ 5%

As stated, of the 14 samples tested, 10 produced reportable results, 2 of which were in the SMPR analytical range. Samples were analyzed between 9 and 15 times each, with most samples analyzed 10 or 11 times. RSDr values ranged from 1.7 – 4.6%, meeting the SMPR requirement, even though the F content of most samples was below the SMPR analytical range. The validation report indicated that liquid samples needed additional homogenization before they could meet the SMPR requirement, and that many powder samples were also treated similarly.

Reproducibility (RSD R ): Requirements:  30 – 100 mcg/100g reconstituted powder: ≤ 15%  100 mcg/100g reconstituted powder: ≤ 10%

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