Quick disclosure up front: I rep for Vyal Labs. The site team asked me to keep this educational, and that works - this applies to any vendor, us included. Everything in this space is RUO (research use only).
Four checks that catch most bad paperwork:
- Batch-matched, not recycled. The lot number on the COA should match the lot number on the vial you receive. A PDF with no lot number, or the same lot number across months of orders, is a red flag. Ask the vendor how you look up the COA for YOUR specific lot before you order.
- A named third-party lab. The report should name an independent analytical lab with a real location you can verify. "In-house tested" means nothing. Bonus move: some labs will confirm a report number by email if you ask - worth doing once with any new vendor.
- HPLC purity AND measured content. Purity (say 98.9%) tells you how much of the material is the target peptide vs impurities. Measured content tells you how much actual peptide mass is in the vial vs the label claim. A report showing only purity is half the picture - a vial can be 99% pure and still be underfilled.
- Heavy metals panel. Arsenic, cadmium, lead, mercury at minimum, with actual results ("Not Detected" or numbers), not blank fields. Not every vendor runs metals on every batch - it is fair to ask which batches have it.
One honest caveat: HPLC is the standard purity method, but it does not confirm sequence identity the way mass spec does. If a vendor claims MS data, ask to see it printed on the report.
Happy to answer questions on reading reports - that is why I am here.