Editorial Review
Author: Dr. Elena Vasquez, Ph.D.(Ph.D. Biochemistry · Lead Science Editor)|Reviewed by: Scientific Compliance Reviewer
Last reviewed: April 2026
Why area percent is not one universal “truth”
HPLC purity is typically reported as area percent of the main peak versus total integrated UV absorbance. That value depends on the method (column chemistry, gradient, detection wavelength) and the integration rules.
Comparing a COA to an internal re-test is only valid if the same or validated equivalent method is used. See also the HPLC glossary entry and the COA reading guide.
Researchers document an acceptance criterion (e.g., ≥ 95% or ≥ 98%) in the study plan before unblinding or execution. That criterion is independent of a retailer’s marketing language on a website.
Linking to orthogonality
Identity confirmation often relies on a second principle such as mass spectrometry. Purity and identity are complementary—a high HPLC % does not, by itself, confirm sequence if identity tests were not run or are out of spec. The companion post mass spectrometry identity on COAs walks through the basics.
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Frequently Asked Questions
“Better” depends on the model’s needs and the impurity profile, not a single headline number. Some applications tolerate specified impurities; others are sensitive to a particular side-product.