How to Read a Peptide Certificate of Analysis (COA)

A real peptide COA names the lot, shows an HPLC chromatogram with a purity percentage derived from peak area, shows a mass-spectrometry result whose measured mass matches the theoretical molecular weight, and comes from a laboratory independent of the seller. If any of those four is missing, treat the number on it as marketing.

What a COA is — and is not

A Certificate of Analysis is a testing laboratory's report on one specific lot of material. It states what tests were run and what they found. It is not a certificate of quality for the product line, the seller, or any other lot — a COA for lot APX-118 says nothing about lot APX-119. That is why the first thing to check is the lot number.

For a research peptide, a complete COA answers two questions: *is this the molecule it claims to be* (identity) and *how much of the sample is that molecule* (purity). Everything else is supporting detail.

Step 1 — Match the lot number

The lot printed on the vial or pen must match the lot on the COA. If a seller shows a single COA for a product regardless of when it was made, it is not batch-specific and does not describe what you received. APX Labs prints the lot on the label and ships the matching COA in the box.

Step 2 — Read the HPLC purity

High-performance liquid chromatography separates the sample into peaks by how fast each component moves through a column. The chromatogram is the graph; the main peak is the target peptide; smaller peaks are impurities — typically deletion sequences, truncated chains, or oxidation products from synthesis [1].

Purity is the main peak's area as a percentage of total peak area. A COA should show the chromatogram (or at least the peak table) and the calculated percentage, not just a number. ≥99% is the standard for research-grade material and is what APX Labs specifies; 95–98% is common in lower grades. Read the HPLC/MS explainer for the method detail.

Step 3 — Read the mass-spectrometry identity

Purity alone can mislead: a sample can be 99% pure and be the wrong peptide. Mass spectrometry measures the molecular mass of the main component and compares it with the theoretical mass of the expected sequence. On the COA, look for the theoretical (calculated) MW next to the observed (found) MW — for BPC-157 that is 1419.5 g/mol. Agreement within instrument tolerance confirms identity. High-resolution MS can also characterise the impurities themselves [2].

Common variations: the observed value may be reported as [M+H]+ (one proton heavier) or as a multiply-charged ion; the COA usually notes this.

Step 4 — Check who ran the test

An independent, named laboratory with its own report format is the strongest signal. A COA generated on the seller's own letterhead with no lab identified is a weaker one. APX Labs uses an independent laboratory for every lot; the lab's report is what ships.

Step 5 — Look at the date and the method

The test date should be close to the lot's production date. The method section should name the technique (RP-HPLC with UV detection at a stated wavelength is typical for peptides) — a COA that says only 'HPLC' with no conditions is thin.

Red flags

• No lot number, or one that does not match your vial.
• A purity number with no chromatogram or peak table.
• No mass-spec result, or an observed mass that does not match the theoretical one.
• Round numbers (exactly 99.0%, 100%) across every product — real results vary lot to lot.
• No laboratory identified.
• The same COA image reused across a seller's product range.

What APX Labs' COA contains

Lot number matching the label; RP-HPLC chromatogram and purity percentage; MS observed vs theoretical mass; test date; the independent laboratory's identification. For blends, each component is reported. See the testing process for how lots move from synthesis to shipment.

A COA documents what a laboratory measured in a sample. It is not a statement about effects, safety, or suitability for any use. APX Labs products are for laboratory research only.

Frequently asked