AOACSPIFANMethods-2017Awards

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1716 Thompson et al.: J ournal of AOAC I nternational V ol. 98, N o. 6, 2015

Table 2. Linearity determination—average of duplicate results from 3 separate days ( n = 3). These determinations were performed after calibration with the standards listed in Table 3 Element Parameter Na a Expected value, mg/L 0.25 0.50 0.75 1.25 1.5 5.0 10 15 30 Overall recovery, % 102.1 104.7 104.0 105.7 105.2 102.4 101.5 100.5 100.1 Overall RSD, % 5.3 2.9 2.1 1.2 1.9 0.6 0.3 1.4 1.4 Mg a Expected value, mg/L 0.10 0.20 0.30 0.50 0.60 2.0 4.0 6.0 12.0 Overall recovery, % 98.9 101.8 103.7 102.9 101.3 100.5 101.1 99.4 99.3 Overall RSD, % 4.6 1.9 2.5 1.8 0.6 0.7 1.6 1.1 1.1 P a Expected value, mg/L 0.25 0.50 0.75 1.25 1.5 5.0 10.0 15.0 30.0 Overall recovery, % 94.8 97.6 93.0 93.4 91.1 93.9 96.1 97.3 93.8 Overall RSD, % 5.9 1.2 7.5 1.3 9.3 8.1 7.8 0.5 8.0 K a Expected value, mg/L 0.50 1.0 1.5 2.5 3.0 10.0 20.0 30.0 60.0 Overall recovery, % 98.2 100.3 101.5 103.1 101.8 102.9 102.2 101.4 100.9 Overall RSD, % 6.9 2.6 3.1 3.7 2.3 3.2 3.2 4.2 4.0 Ca a Expected value, mg/L 0.50 1.0 1.5 2.5 3.0 10.0 20.0 30.0 60.0 Overall recovery, % 97.8 99.9 100.5 102.1 100.7 100.9 102.1 100.6 101.1 Overall RSD, % 5.5 2.5 1.8 3.0 1.1 2.7 3.2 3.7 3.0 Cr a Expected value, μg/L 0.40 0.80 1.2 2.0 2.4 8.0 16.0 24.0 48.0 Overall recovery, % 100.2 100.1 102.0 101.5 103.0 101.8 101.5 100.9 98.9 Overall RSD, % 7.2 5.4 0.5 1.6 1.8 1.0 0.6 1.2 2.7 Mn a Expected value, mg/L 0.0025 0.005 0.0075 0.0125 0.015 0.050 0.10 0.20 0.30 Overall recovery, % 99.9 101.1 101.7 102.3 101.9 101.9 102.4 101.4 99.6 Overall RSD, % 5.8 3.1 1.2 1.2 0.8 1.5 1.6 1.2 1.2 Fe a Expected value, mg/L 0.025 0.050 0.075 0.125 0.15 0.50 1.0 1.5 3.0 Overall recovery, % 105.0 106.1 106.7 106.5 106.6 105.5 104.7 99.4 98.3 Overall RSD, % 8.9 7.1 4.1 2.9 3.3 4.3 5.0 1.7 1.4 Cu a Expected value, mg/L 0.0025 0.005 0.0075 0.0125 0.015 0.050 0.10 0.20 0.30 Overall recovery, % 101.6 101.9 101.1 102.9 101.9 101.6 100.4 99.3 96.3 Overall RSD, % 6.8 6.1 3.2 2.8 2.8 1.9 1.8 3.0 3.1 Zn a Expected value, mg/L 0.010 0.020 0.030 0.050 0.060 0.20 0.40 0.60 1.2 Overall recovery, % 98.6 100.6 99.5 101.1 100.6 99.7 101.2 100.0 98.1 Overall RSD, % 7.6 6.6 1.9 2.1 2.9 2.0 1.5 2.0 2.0 Mo a Expected value, μg/L 0.40 0.80 1.2 2.0 2.4 8.0 16.0 24.0 48.0 Overall recovery, % 97.7 101.2 103.7 98.3 100.7 100.7 100.6 99.7 98.8 Overall RSD, % 7.5 2.9 4.0 3.5 0.8 1.3 1.2 2.2 2.2 Se b Expected value, μg/L 0.20 0.40 0.60 1.0 1.2 4.0 8.0 12.0 24.0 Overall recovery, % 100.0 97.3 98.2 96.6 99.4 100.0 99.0 99.4 99.9 Overall RSD, % 3.4 2.8 2.0 3.3 1.4 1.2 0.5 2.2 1.2 a  He gas mode; Ge ISTD. b  H 2 gas mode; Te ISTD.

Precision data from SRM 1849a are shown in Table 5. The SRM was analyzed nine times, on different days and yielded RSD iR of <3% for all elements.

unfit for validation work. Most elements demonstrated RSD iR <5% for all matrixes, which is quite remarkable considering the opportunities for variability in the study design. There is no SMPR for intermediate precision, but these data suggest that the method would perform well in a collaborative study, and this proved to be the case ( see below). The cases for Fe, Cu, and Mn are discussed under LOQ. There were no SPIFAN matrixes that really challenged the method anywhere near the required lower analytical range for these elements, and no low-level spikes were performed.

Recovery/Accuracy

The SMPR designates a recovery of 90–110% over the range of the assay, and 80–115% for low levels of Mn. Table 6 shows the recovery of each element in each SPIFAN matrix measured in triplicate over each of 3 days. The spikes were added at approximately 100% of the nominal element concentration, and the triplicate means on each day were averaged to one result