Evaluating a Research Peptide Vendor: A Checklist

The research-peptide market is uneven. The same molecule can be sourced from a supplier that provides batch COAs, third-party testing, and cold-chain shipping — or from one that provides none of the above. Here is the checklist we would use.

1. Is every batch third-party tested?

In-house purity claims are not verifiable. Look for a named third-party analytical lab (e.g., Janoshik Analytical, Finnrick, Certified Peptides) on every COA.

2. Does the COA include endotoxin data?

Endotoxin is quietly the most common gap. If you plan any cell-based work, an unreported endotoxin value is disqualifying.

3. Can you match a vial back to a batch?

Every vial should carry a batch number that resolves to a specific COA on the supplier's site. If it does not, the paperwork does not describe your material.

4. What is the stated purity method?

HPLC ≥99% at 220 nm is the working standard. Anything else needs explanation.

5. Is identity confirmed by mass spectrometry?

Purity without identity is meaningless. A legitimate COA reports observed vs. theoretical MW.

6. How does the material ship?

Lyophilized peptides are heat-tolerant for short transit but should ship in insulated packaging with the option of cold-chain for temperature-sensitive sequences.

7. What does the label say?

Every vial should read "For Research Use Only — Not for Human Consumption." A supplier that hides this is not operating within RUO norms.

A supplier that answers all seven cleanly is not necessarily the cheapest. It is the one whose data you can actually rely on.