Every reputable research peptide supplier talks about Certificates of Analysis. Far fewer explain how to actually read one. This guide walks through what a COA is, section by section, so you can evaluate the documentation behind any research compound — ours or anyone else's — with a critical eye.

Important: This article is educational guidance on quality documentation for laboratory research materials. All research peptides are for laboratory research use only — not for human consumption.

What a COA Is (and Isn't)

A Certificate of Analysis is a document reporting the results of analytical testing performed on a specific batch of material. A genuine COA answers two questions:

  1. Identity — is this material actually the compound it claims to be?
  2. Purity — how much of the material is that compound, versus impurities?

What a COA is not: a marketing badge. A supplier displaying the word "COA" or a generic certificate not tied to a specific batch is offering reassurance, not evidence. The document only means something when it connects a named batch to real test results from an identifiable testing process.

The Sections That Matter

1. Batch / Lot Number

The single most important field. The COA must state the batch it applies to, and that batch number should match what's on the product you receive. A COA without a batch number — or one that never changes across months of stock — is a template, not a test.

2. The Compound's Identity

Look for the compound name and, ideally, supporting identity data:

  • Molecular weight — every peptide has a known theoretical mass. The COA should report a measured mass consistent with it. A meaningful mismatch means the material may not be what's claimed.
  • Mass spectrometry (MS) data — the standard method for confirming a peptide's identity. A measured mass matching the theoretical mass (within reasonable instrument tolerance) is the cornerstone of identity confirmation.

3. Purity — and How It Was Measured

A percentage alone ("99%") is a claim. A percentage plus the method is a result. The standard method for peptide purity is HPLC (High-Performance Liquid Chromatography), which separates the components of a sample and quantifies the main peak against impurities.

Better COAs include the chromatogram itself — the actual trace showing the main peak. You don't need to be a chemist to apply the basic logic: one dominant, clean peak suggests a pure sample; a forest of significant secondary peaks suggests impurities.

Be precise about what the number means: "≥99% purity by HPLC" refers to the chromatographic purity of the peptide content. It is a statement about that batch as tested — which is exactly why batch-specific documentation matters.

4. Who Did the Testing

There's a meaningful hierarchy of credibility:

  • Independent third-party laboratory — strongest. The tester has no stake in the result.
  • Manufacturer's own QC testing — common and not worthless, but unverified by anyone outside the supply chain.
  • No stated tester at all — a document with no identifiable origin carries little evidential weight.

A supplier who pays an independent lab to verify their material is making a costly, checkable commitment to quality. That commitment is itself a signal.

5. Dates

Testing has a date. A COA from years ago tells you about material from years ago. For a current batch, expect reasonably current testing.

Red Flags — When to Walk Away

  • No batch number, or a "COA" that's identical for every product and never updates
  • Purity claims with no method stated (a number with no HPLC/MS behind it)
  • No chromatogram or data, just a typed percentage on a letterhead
  • No identifiable testing source — neither an independent lab nor even the manufacturer named
  • Implausible perfection — every product, every batch, always exactly "99.9%", forever
  • A supplier who can't or won't show a COA when asked — for a research-grade supplier, this documentation is the product

A Worked Habit for Researchers

When evaluating any supplier, make this the routine: find the product → find its batch number → find the COA for that batch → check identity (MS, molecular weight), purity (HPLC, ideally with the trace), tester, and date. Two minutes of checking separates documented material from marketed material.

For the broader picture of evaluating suppliers — company registration, storage, responsible sales practice — see our guide to choosing a UK research peptide supplier.

COAs at Peptide HQ

Peptide HQ publishes batch Certificates of Analysis on our site, with purity independently verified by a third-party laboratory using HPLC and mass spectrometry. We'd rather you check our documentation than take our word for it — that's the point of publishing it.

All products are for laboratory research use only and are not for human consumption.