Peptide Purity & COA: How to Verify Research Peptide Quality

Understand purity grades, HPLC, mass spectrometry and how to read a Certificate of Analysis before you buy research peptides.

Published October 30, 2026 · PepNova technical team

Why purity matters in research

For any peptide-based experiment, purity directly affects reproducibility. Impurities such as truncated sequences, deletion peptides or residual solvents can skew binding assays, cell assays and in-vivo readouts. That is why a verified purity value — not a marketing claim — should sit at the center of every purchasing decision.

How peptide purity is measured

• Reversed-phase HPLC (RP-HPLC) — the standard method, reporting the area-% of the main peak versus total detected peaks.
• Mass spectrometry (MS / LC-MS) — confirms the molecular weight and identity of the target peptide.
• Amino-acid analysis (AAA) — verifies composition and can cross-check purity.
• Residual solvents & heavy metals — tested against limits for safety and consistency.

How to read a Certificate of Analysis (COA)

A credible COA should state, at minimum: batch/lot number, peptide name and sequence, appearance, measured purity by HPLC, water/content, residual solvent results, storage condition, and the test date. Match the lot number on the COA to the vial you receive.

Common purity grades

• Crude (<80%) — unsuitable for most assays; used only for screening or non-critical work.
• ≥95% — acceptable for many binding and biochemical studies.
• ≥98% / ≥99% — recommended for quantitative, cell-based and in-vivo research.

What PepNova provides

Our standard research peptides are typically ≥99% by HPLC, with COA, chromatogram and MSDS on every batch. Third-party testing is available on request.

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