Understanding Certificates of Analysis (COA) for Research Peptides

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What a Certificate of Analysis Is

A Certificate of Analysis (COA) is a batch-specific document that reports the analytical testing performed on a research peptide. It is the single most important tool a researcher has for verifying that the material in a vial matches what was ordered — in identity, purity, and composition. A credible supplier publishes a COA tied to the exact lot number on the vial.

The Core Sections of a COA

• Product & lot identification — the peptide name, sequence or molecular formula, and a unique batch/lot number that should match the vial label.
• HPLC purity — High-Performance Liquid Chromatography separates the sample into its components. The chromatogram shows a dominant peak for the target peptide; the reported purity (e.g., ≥99%) is the area of that peak relative to all detected peaks.
• Mass Spectrometry (MS) — Confirms molecular identity by measuring the mass-to-charge ratio. The observed mass should match the theoretical mass of the intended sequence.
• Net peptide content / water content — Reports how much of the vial mass is actual peptide versus residual water, salts, or counter-ions.
• Appearance and additional tests — May include sterility, endotoxin, or heavy-metal screening depending on the product.

How to Read an HPLC Chromatogram

Look for one tall, sharp, well-resolved peak. Small satellite peaks represent impurities such as truncated or oxidized sequences. The narrower and cleaner the main peak — and the smaller the satellites — the higher the purity. Reputable COAs print the retention time and the integrated area percentages.

Red Flags

• A generic, undated COA not linked to a specific lot number
• Missing MS data (purity without identity confirmation is incomplete)
• Chromatograms with multiple large peaks reported as high purity
• No way to independently verify the document with the supplier

At PX1 Research, every batch is verified by HPLC and mass spectrometry, with a lot-linked COA available for the material you receive.