Protocol4 min read
Why we third-party test every lot
A peptide's purity claim is only as good as the assay behind it. Here's how our COA workflow works and what to look for in any peptide supplier.
Purity is the single most important quality attribute of a research peptide. A peptide catalogued as 99% pure can behave completely differently from one at 95% if the residual 4% includes truncated sequences or metal salts that interact with the biological pathway being studied.
Our testing workflow
Every production lot at Purity Peptides is analysed by an independent contract laboratory using two orthogonal techniques:
- **Reverse-phase HPLC** to quantify the target peptide and detect closely-eluting impurities.
- **Mass spectrometry (LC-MS or MALDI)** to confirm molecular weight and identify any deletion or oxidation products.
A signed Certificate of Analysis (COA) is attached to the lot record and made available on request via your order confirmation email.
Questions to ask any supplier
- Is the COA lot-specific, or a generic marketing PDF?
- Is the testing lab named on the COA?
- Does the COA include both HPLC and MS traces?
- What is the endotoxin limit?
Written by The Purity Peptides team. For laboratory research use only.