What a COA is (and is not)
A Certificate of Analysis is a lot-level lab report. It describes one manufactured or tested batch — not every future bottle of that product name, and not a clinical dossier. For research peptides, the COA is how you confirm that the material you received matches what the supplier claimed for that lot.
It is not medical advice, not a safety data sheet by itself, and not permission to use the compound outside a laboratory setting. Nextday Peptides sells Research Use Only materials; COAs support analytical and experimental documentation, not human or veterinary use.
Start with the vial, then open the PDF
Before you dig into chromatograms, confirm the paperwork belongs to the bottle you are holding. Match product name or catalog identifier, stated strength or fill (for example 5 mg or 10 mg), and — most important — the batch or lot number printed on the label.
If the lot on the vial does not appear on the COA, stop and request the correct file. Our COA Library is searchable by compound and batch; if a lot is missing, email orders@nextdaypeptides.com with the order number and the batch printed on the label.
Fields most labs check first
Formats vary by testing lab, but research-peptide COAs commonly include some combination of the following. Treat missing critical fields as a reason to ask questions, not as something to ignore.
- Product or compound name (and sometimes CAS or sequence)
- Batch / lot number tied to the vial label
- Appearance (for example white lyophilized powder)
- Assay or purity by HPLC (often reported as ≥99% or a measured %)
- Identity method (HPLC retention time match, MS, or both)
- Test date and lab identity or accreditation note, when provided
Reading the HPLC purity line
HPLC purity answers a narrow question: of the peaks the method detects under stated conditions, what share is attributed to the main analyte? A high percentage is useful for many in-vitro workflows, but it is only as good as the method and the sample preparation behind it.
Compare the reported value to the product page claim (we typically publish ≥99% HPLC for research peptides). If the COA shows a measured percentage, note that number in your lab notebook alongside the lot. For a deeper look at what that figure does and does not mean, see our HPLC purity article.
Identity vs purity
Purity does not prove identity by itself. A clean chromatogram still needs a stated identity check — often mass spectrometry, a reference retention time, or both. When both appear on the COA, you have stronger lot documentation than purity alone.
If you are comparing synonyms across catalogs (for example Epitalon vs Epithalon), rely on sequence, CAS, and the COA identity section rather than marketing names alone.
Limits worth keeping in mind
A COA reflects the tested sample and method. It does not replace your institution’s receiving procedures, solubility checks, or in-house confirmation when a protocol requires it. Storage after arrival still matters; a correct COA will not rescue a vial that sat warm on a loading dock for a week.
Third-party lab names and methods can change over time. Prefer the file for your exact lot over an older PDF for a different batch of the “same” SKU.
Using the Nextday Peptides COA Library
Browse the COA Library on this site to pull batch documents for compounds we stock. Availability varies by product and lot. Keep COAs with your experimental records, and treat them as research documentation only — consistent with our Educational Articles Disclaimer and Research Use Only terms.