5. AOACSPDSMethods-2018AwardsV3

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K oshy et al .: J ournal of AOAC I nternational V ol . 99, N o . 6, 2016  1449

B

A

Figure 2. Chromatograms of methanolic extract (WS/06Lot10) sample using (A) UV detection and (B) PDA detection.

in duplicate at three extraction weights, the repeatability was <2.2% for peak area and <1% for retention time (Table 9). Content.— Repeatability precision based on the determination of content (% w/w) of each analyte was evaluated in two experiments. In the first experiment, each of the eight study samples was extracted and the resulting sample solution analyzed in triplicate. The results are shown in Table 10. Seven of eight samples demonstrated a repeatability of <3% for each of the six analytes, as well as the sum of withanolides, meeting the acceptance criteria of SMPR 2015.007. In two cases, WS/06Lot08 and RD/1170, the sum of withanolides was >1% w/w and the repeatability slightly exceeded the acceptance criterion of ≤1%. The eighth sample, WS/05Lot20, yielded RSD r values as high as 10.8% for withanolide B and <7% for the remaining five analytes and the sum of analytes. This sample is the only water extract sample tested, and the withanolide content is the lowest of all samples tested, including the raw materials. Compared with the SMPR requirements, the repeatability values of withanolide B and 12-deoxywithastramonolide are

greater than the allowed variability, but the four other analytes were within the acceptance criteria. In the second experiment, the full method including methanol extraction was replicated three to four times at five sample weights, and each sample extract was analyzed once (Table 11). Not surprisingly, the RSD r (%) of the full method, including all sample weights, was somewhat higher than the repeatability of replicate injections of a single extract in the first experiment. RSD r values varied from 0.83 to 2.01% across all analytes and the sum of the analytes, meeting the acceptance criteria of RSD r ≤1% at >1% w/w, ≤4% at >0.1–1% w/w, and ≤6% at >0.01–0.1% w/w.

Recovery

Recovery of total withanolide content after spiking is shown in Table 12. Materials spiked prior to extraction (WS/05Lot21, WS/06Lot10, RD/1170, and RD/1162) demonstrated recoveries ranging from 90.5 to 104.7%. With total content of each

A

B

Figure 3. Chromatograms of raw material (ERH-046) sample using (A) UV detection and (B) PDA detection.