If you've spent any time sourcing research peptides, you've seen the term "COA" attached to nearly every product listing. Few documents matter more for evaluating a supplier — and few are as widely misunderstood.
A Certificate of Analysis is the actual laboratory report confirming what's in a vial: what compound it is, how pure it is, and how a third-party lab arrived at those numbers. It's the difference between a supplier's marketing claim and independently verified data. This guide walks through what a real COA contains, how to interpret each section, and what to watch for when one looks incomplete.
What a COA Actually Is
A Certificate of Analysis is a document issued by a testing laboratory — ideally one independent from the seller — reporting the results of specific analytical tests run on a sample from a particular production batch. It is not a marketing document. A properly issued COA is generated by the lab itself, references its own equipment and methodology, and is traceable to a specific batch or lot number.
This last point matters more than it might seem. A COA that isn't tied to a specific batch number is really just a report on a sample tested at some point — not necessarily the one in the vial you're holding.
The Core Sections of a COA
1. Identity Testing
Before purity means anything, a lab has to confirm the sample actually contains the compound it's labeled as. This is typically done via mass spectrometry (MS), which measures the molecular weight of the sample and compares it against the expected value for the target compound. A mismatch here means the vial doesn't contain what the label says — regardless of how clean the rest of the report looks.
2. Purity (HPLC)
High-Performance Liquid Chromatography is the standard method for measuring purity. In simple terms, HPLC separates a sample into its individual components as they pass through a column, and measures how much of the total sample corresponds to the target compound versus anything else — leftover synthesis byproducts, degradation products, or contaminants.
The result is usually expressed as a percentage (e.g., "99.4% purity"). This number reflects how much of the sample is the intended compound, not a measure of safety or effectiveness — it's strictly a chemistry metric describing sample composition.
3. Mass and Volume Verification
Some COAs include a separate check confirming the actual quantity of material in the vial matches the labeled amount (e.g., that a vial labeled 10mg genuinely contains close to 10mg). This is a distinct test from purity — a sample can be highly pure while still being under- or over-filled.
4. Endotoxin Testing (when included)
Endotoxins are byproducts of bacterial cell walls that can remain in a sample depending on manufacturing conditions. Endotoxin testing (often via a Limulus Amebocyte Lysate, or LAL, assay) measures this specifically. Not every batch will have this test performed — it's a more specialized, often more expensive analysis — so its presence or absence is worth noting rather than assuming.
5. Batch Number and Testing Date
A real COA references the specific batch or lot number it applies to, and the date testing was performed. Without this, there's no way to confirm the report actually corresponds to the product you're purchasing rather than an earlier or different batch entirely.
What a Trustworthy COA Looks Like
- Issued by a named, independent third-party laboratory — not the seller's own internal testing
- Tied to a specific, verifiable batch number that matches what's printed on the product
- Includes a clear identity test result (mass spec or equivalent), not purity alone
- States its testing date, so you can judge how current the data is
- Available before purchase, not only provided after a customer asks
Common Red Flags
- No batch number. A COA that can't be tied to the specific product you're buying tells you very little about that product.
- Purity only, no identity test. A high purity percentage means nothing if the lab never confirmed the sample is actually the labeled compound.
- Testing performed by the seller itself, with no independent lab named. This isn't necessarily dishonest, but it removes the independent verification that gives a COA its value in the first place.
- Suspiciously uniform results across many different products or batches. Real testing data has natural variation; identical numbers repeated across unrelated products are worth questioning.
How We Approach This at Pacific Peptides
Every product we carry is tested for purity by an independent laboratory. Where mass and endotoxin testing have also been completed, we publish those results too — and where they haven't, we say so rather than leaving a gap that could be misread as a passed test. Batch numbers appear only when they genuinely exist for that product; we don't generate placeholder numbers to make a listing look more complete than the underlying testing supports.
You can view the actual COAs behind our current catalog, batch numbers included, on our Lab Results page — every document is the real report, not a summary of one.
This article is for general research and educational purposes. It does not constitute guidance for human use of any compound. All products referenced are sold strictly for laboratory research use.