28 Aug What HPLC Purity Results Can and Cannot Tell You
HPLC Purity Results: What the Percentage Actually Means
A chromatogram showing a dominant peak and a reported purity of 98% or 99% can look like a very complete analytical result. It is certainly useful information, but the number needs to be interpreted in the context of the method that produced it. High-performance liquid chromatography, or HPLC, is widely used to separate and measure components within a sample. The technique can provide valuable information about composition and relative detector response, but an HPLC purity percentage is not a universal measurement of everything present in a material. Understanding that distinction helps prevent a useful analytical result from being asked to support conclusions it was never designed to establish. A more detailed discussion of what HPLC can and cannot establish helps show why chromatographic purity, molecular identity, and overall sample characterization should not be treated as interchangeable conclusions. According to FDA guidance on analytical procedures and methods validation, a validated analytical method must demonstrate specificity — meaning it must be able to assess unequivocally the analyte in the presence of other components — which is a separate requirement from simply reporting a high area percentage.
[caption id="attachment_75792" align="aligncenter" width="500"] Photo by Jess Loiterton[/caption]