A Certificate of Analysis (COA) is the single most useful document a peptide supplier can give you. It is batch-specific evidence that the material you are buying meets its specification. Learning to read one quickly protects you from off-spec deliveries and helps your QC team sign off faster.
What every COA should contain
- Product name, INCI and CAS number — must match your purchase order.
- Batch / lot number, manufacturing date and retest or expiry date — the batch must match the drum you actually receive.
- Appearance — e.g. "white powder" or "blue crystalline powder".
- Identity — confirmation by a method such as MS (mass spectrometry) or IR.
- Assay / purity — usually by HPLC, reported as a percentage against a stated method and acceptance limit (e.g. ≥ 98% by HPLC).
- Water content — often by Karl Fischer (KF).
- Residual solvents — by GC, against ICH Q3C limits.
- Heavy metals / elemental impurities — against ICH Q3D where relevant.
- Microbiological — total aerobic count (TAMC), yeast/mould (TYMC) and absence of specified pathogens.
- Single/largest impurity — a maximum for any individual related substance.
- Storage conditions.
The buyer's five-minute checklist
- Does the CAS and product name match your order exactly?
- Is purity reported by HPLC, with the method named — not just a bare number?
- Does every result sit inside the stated acceptance limit?
- Is there a batch number, and will it match the label on the shipped goods?
- Is there a retest/expiry date, and is the material well within it?
Go one step further
For high-value peptides, ask for the actual HPLC chromatogram, not just the summary figure — a clean single main peak is what you want to see. Request the MSDS/SDS for safe handling and the TDS (Technical Data Sheet) for formulation guidance. Cross-check the COA against the supplier's published spec sheet; the two should agree.
If a supplier cannot produce a batch-specific COA with an HPLC assay and a stated method, treat that as a red flag.
WYOO is a sourcing partner with audited partner factories, not a manufacturer. We issue a batch-specific COA and MSDS with every shipment, send the COA before you pay, and provide HPLC data, TDS and third-party testing on request. Standard terms are MOQ 50 g, lead time 5 to 10 working days after payment for in-stock lots, T/T with 30% deposit and 70% before shipment for B2B accounts, and free 5 g samples for qualified companies; quotes are given in English, Chinese, Spanish, German or French. Ask us for a sample COA before you order so your QC team knows exactly what to expect.
Frequently asked questions
- What is the difference between a COA and a specification sheet?
- A specification sheet lists the acceptance limits a product is supposed to meet; a COA reports the actual measured results for one specific lot against those limits. Always compare the two: the COA must carry a lot number, the test methods and dated results, or it is not a release document.
- Can I see the COA before I pay for a peptide order?
- Yes, and you should insist on it. WYOO sends the batch COA and MSDS before payment, provides the HPLC chromatogram and TDS on request, and can arrange a third-party test on the same lot. Standard terms are MOQ 50 g, 5 to 10 working days after payment for in-stock lots, and T/T with 30% deposit and 70% before shipment.
- What are the most common red flags on a peptide COA?
- A purity figure with no method named, no lot number or a lot number that does not match the label, results outside the stated limits, a missing retest or expiry date, and a CAS or product name that differs from your purchase order. Any of these should stop the order until the supplier explains.