What Purity Should a Peptide Have? HPLC Purity Explained

Research-grade peptides are commonly reported at 98 to 99 percent purity or higher by HPLC. But purity is only part of the picture: HPLC does not measure salts, water, endotoxins or heavy metals, and identity must be confirmed separately by mass spectrometry.

What purity should a peptide have: chromatography instrument with sample vials
Short answerResearch-grade peptides are commonly reported at 98 to 99 percent purity or higher by HPLC. But purity is only part of the picture: HPLC does not measure salts, water, endotoxins or heavy metals, and identity must be confirmed separately by mass spectrometry.

What HPLC Purity Measures

High-performance liquid chromatography (HPLC) separates a sample into its parts. A clean peptide shows one large peak, and purity is that peak's share of the total peptide-related material. It detects the target peptide and peptide-related impurities, such as by-products of synthesis.

What HPLC Purity Does Not Measure

  • Identity: a pure sample of the wrong peptide still passes. Mass spectrometry confirms the molecular weight.
  • Salts, water and fillers: these are not shown as peptide impurities
  • Endotoxins and heavy metals: these need their own tests
  • Net peptide content: the actual amount of peptide in the vial

How to Check a Purity Claim

Ask for a lot-matched certificate of analysis from an independent laboratory with the chromatogram attached, the lot number matching your vial, a recent test date and a mass spectrometry result. See how to read a COA and our lab testing guide.

Keep Learning

Browse the peptide library, compare peptides and read plain-English guides on lab testing and Canadian rules.

Explore the Library →
FAQ

More Questions

Is 99% purity good for a peptide?

Yes, 98 to 99 percent or higher by HPLC is a common standard for research-grade peptides, as long as identity is confirmed by mass spectrometry and the report matches the lot.

Does 99% purity mean the vial is 99% peptide?

Not exactly. HPLC purity is the share of peptide-related material that is the target peptide. It does not account for salts, water or other non-peptide content.

How do I verify peptide purity?

Check a lot-matched third-party COA with the HPLC chromatogram and mass spectrometry result, and confirm the lot number on your vial matches the report.

Related: All peptide FAQs · Peptide Library · Peptides A-Z · COA Library · Contact

Educational information only, not medical or legal advice. Information on this site is educational only and is not medical advice.