Part VII. Verifying the Analytical Method's Accuracy

Investigation 31: Extraction Yield for Other Analytes

Table 3 summarizes the predicted extraction yields for the remaining compounds in Danshen. The predicted extraction yields for lithospermic acid, salvianolic acid A, cryptotanshinone, tanshinone I, and tanshinone IIA are from the empirical models used to construct the response surfaces in Figures 11–15; the predicted extraction yields for rosmarinic acid and for dihydrotanshinone are the average results of the 13 trials used in their respective central-composite designs.

Table 3. Predicted Extraction Yields for Danshen's Constituents
analyte extraction yield (mg/g) analyte extraction yield (mg/g)
danshensu (see investigation 30) dihydrotanshinone 0.424
rosmarinic acid 2.317 cryptotanshinone 0.917
lithospermic acid 2.657 tanshinone I 1.336
salvianolic acid A 0.600 tanshinone IIA 2.762

Investigation 31. Figure 18 shows the chromatogram for a sample of Danshen extracted using the optimized conditions from Part VI. Using this chromatogram, calculate the actual extraction yield for each analyte and report its experimental extraction yield as a percentage of its predicted extraction yield from Table 3. (You may recall that in Investigation 6 you determined the relationship between absorbance and concentration for each analyte.) Do your results provide confidence in our analytical method? Why or why not?