I am quantifying plant metabolites in extracts using HPLC. The literature cites two methods to validate my process, namely- Extraction Efficiency and Percent recovery. While reading the literature I have notices that for one, you spike the sample with a known concentration of metabolite that is already there in the extract but for the other you need to spike with a known concentration of similar compound which is not present in the extract. Is that correct? Is there any book that explains the differences between the two?
percent recovery normally describes total recovery of the method. Including extraction, purification and solvent evaporation of exchange. Extraction efficiency is normally analyte removal from a matrix by for a single extraction. Thus is you extracted a sample twice and each extraction had 70% efficiency you would have a theoretical recovery of (1-0.3^2)=0.91 or 91%, before you began clean-up and solvent concentration/exchange.
However, be careful with my explanation. The authors and reviewers of the article might not have been this detailed in preparing and evaluating the method that you mention.
In addition, if we have (A) known analyte in mobile phase solution, (B) Pre-spiked analyte sample and (C) Post-spiked analyte sample, then
The extraction recovery = B/A x 100%
The extraction efficiency or process efficiency = B/A x 100%
The matrix effect = C/A x 100%
Hope it helps.
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