Reconstituting a lyophilized peptide correctly is one of the most important steps in any research protocol. Use too much or too little bacteriostatic water, and your concentration math (and your results) can be thrown off before you even start. Here's a clear walkthrough of the process our research team follows.
How to Read a Peptide COA: A Researcher's Guide to Certificates of Analysis
A Certificate of Analysis (COA) is the single most important document that comes with a research peptide order, yet it's also one of the most overlooked. Knowing how to read one — and what to look for — turns an unfamiliar lab report into a clear signal of quality and identity. Here's a practical breakdown of what every COA should tell you.
Why the COA Matters
A COA is an independent (or manufacturer) lab's record of what's actually inside a vial, confirming both identity and purity through analytical testing rather than taking a label at face value. Without this documentation, there's no way to verify that a peptide is what it claims to be, at the concentration and purity stated. For any serious research protocol, treating the COA as a required document rather than an optional extra is the difference between reliable data and guesswork.
Key Fields on Every COA
Most COAs include a batch or lot number that ties the document to a specific production run, along with the test date and the peptide's stated purity percentage. High-quality COAs also report the analytical method used, most commonly HPLC (High-Performance Liquid Chromatography) for purity and mass spectrometry (MS) for identity confirmation. Look for a clear match between the lot number printed on the vial label and the one listed on the COA — a mismatch here is an immediate red flag.
How to Verify Purity and Identity Results
Purity is typically reported as a percentage, and reputable suppliers in the research peptide space generally report results at 98% or higher. The HPLC chromatogram, when included, should show a single dominant peak with minimal shoulder peaks or noise, indicating few contaminants or degradation products. Mass spec results should show a molecular weight that matches the expected value for the peptide in question, confirming that the correct sequence was synthesized.
Red Flags: When a COA Should Raise Questions
A COA that lacks a lot number, test date, or named testing lab offers little real verification and should be treated with caution. Watch for generic or templated-looking documents that appear identical across completely different products, as well as purity values reported without any supporting chromatogram or raw data. If a supplier is unwilling to provide a COA for a specific batch, or provides one that doesn't match the lot number on the vial, that's reason enough to look elsewhere.
A Quick COA Checklist Before You Order
Before finalizing an order, confirm that a COA is available for the specific batch being shipped, not just a generic product-level document. Check that the lot number, purity percentage, and test date are all clearly listed, and that HPLC and mass spec data (or at least a summary of methods used) are included. Keep COAs on file alongside your lab records for every batch you use, so results stay traceable if questions come up later.

