How to Read a Peptide Vial COA: HPLC Purity, MS Identity, Endotoxin and Fill
What each line of a batch certificate of analysis tells you, how to match the COA to the vials you received, and what to compare it with on the product page — with Acetyl Octapeptide-3 as the example.
Published October 9, 2026 · 5 min read · Pepoderma
Every lot of our stocked peptides has a batch certificate of analysis (COA) that reports four tests: HPLC purity, MS identity, endotoxin and fill. Here is how to read each one and what to compare it with.
1. Lot number, product and strength
Start with the header. The lot number on the COA is the lot we ship, and the product and strength must match your order line — for example Acetyl Octapeptide-3, 10 mg. Ask for the COA of the batch you are quoted before you order.
2. HPLC purity
High-performance liquid chromatography separates the peptide from related impurities; the result is the peptide's share of the measured peak area, in %. Compare it with the specification on the product page (≥ 99.0% for Acetyl Octapeptide-3 in our product table). The specification is the minimum; the measured value is on the COA.
3. MS identity
Mass spectrometry confirms that the main component has the expected mass. Compare it with the molecular weight on the product page and the form it refers to: a free peptide, a salt or a copper complex give different values (see why CAS numbers and molecular weights differ). For Acetyl Octapeptide-3 the product table gives 1075.2 g/mol; a result about 186 lower would point to Acetyl Hexapeptide-8.
4. Endotoxin
The endotoxin result is reported on every batch COA of a stocked peptide, with its unit and method as the COA states them. Compare lots by the reported value and unit, not by a pass mark from another document.
5. Fill
Fill is the amount of peptide per vial. Compare it with the strength on the label and on your order line.
A third-party report as a cross-check
For several of our peptides — Acetyl Octapeptide-3 among them — there is an independent HPLC and MS analysis by a third-party laboratory in Tianjin. Low-resolution previews of the first pages are on the Batch COA page and the product pages, and sales send the complete report — compare how the same two methods appear in an outside report.
Checklist
- Lot number, product and strength match the order line.
- HPLC purity at or above the specification.
- MS identity consistent with the molecular weight and its form.
- Endotoxin reported, with unit.
- Fill consistent with the strength.
Other tests are agreed in writing before the order. See what every batch COA reports.
Talk to sales
Want the COA of the batch you are quoted?
Name the peptide and strength; we reply within 24 hours with the quotation and the batch COA.
Peptides in this guide
- Acetyl Octapeptide-3 · stocked
- GHK-Cu · stocked
- Palmitoyl Pentapeptide-4 · stocked
Trade names in this guide (for example SNAP-8®, Argireline®, Leuphasyl®, Eyeseryl® — Lipotec, Lubrizol; Matrixyl® — Sederma, Croda; SYN®-AKE — dsm-firmenich) are trademarks of their owners and are used only to identify the peptides. Pepoderma lists peptides by chemical name and is not affiliated with these companies. All products are supplied for research use only.
Frequently asked questions
- What four tests are on every batch COA?
- HPLC purity, MS identity, endotoxin and fill — for every lot of a stocked peptide.
- What should the MS identity be compared with?
- With the molecular weight on the product page and the form it refers to (free peptide, salt or copper complex).