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HPLC Purity vs Net Peptide Content

Chromatographic purity is a share of detector response. Net peptide content is a share of mass. They answer different questions and are often not both present.

Therapept EditorialUpdated 12 September 20267 min readReviewed by Therapept Editorial
Two numbers, two quantities
ResultTypical methodUnit of the percentage
HPLC purityRP-HPLC, UVPeak area
Net peptide contentAmino-acid analysisSample mass

Why they diverge

Counterion (often TFA) and water contribute mass and little UV area at the peptide wavelength. A lot can be high by area and substantially lower by mass. If content is not reported, do not infer it.

Sources

  1. ICH Q2(R2) — Validation of Analytical Procedures
  2. Glossary — chromatographic purity

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