Understanding HPLC Purity and Certificates of Analysis
HPLC (High-Performance Liquid Chromatography) is the industry-standard method for measuring peptide purity — a 99% result means 99% of the material is the intended compound. A Certificate of Analysis (COA) is the batch-specific lab document reporting that purity, along with mass-spec identity confirmation, endotoxin testing, and a batch number. Independent third-party testing is more trustworthy than vendor self-testing.
When sourcing research peptides, purity verification separates reliable material from unknowns. The two documents that matter most are the HPLC purity result and the Certificate of Analysis (COA).
What is HPLC?
High-Performance Liquid Chromatography (HPLC) separates the components of a sample to quantify how much of it is the target peptide versus impurities. A result of "99% purity" means 99% of the material is the intended compound. HPLC is the industry-standard method for peptide purity verification.
What is a Certificate of Analysis (COA)?
A COA is a lab-issued document reporting the test results for a specific batch. A thorough COA includes:
- HPLC purity percentage
- Mass spectrometry confirmation of molecular weight (identity)
- Endotoxin testing (important for sterile research applications)
- Batch/lot number so the certificate maps to the exact product you received
How to read purity results
| Purity | Interpretation |
|---|---|
| ≥99% | High-grade research material |
| 98–99% | Good, common for complex/blended peptides |
| <98% | Higher impurity fraction — scrutinize the COA |
Why third-party testing matters
A vendor testing its own product has an incentive to report favorable numbers. Independent third-party verification (from an accredited lab) provides an unbiased check. Seqra provides HPLC certificates and independent third-party verification on its compounds.
View Seqra certificates of analysis →Verified compounds
Key takeaways
- HPLC separates a sample to quantify how much is the target peptide vs impurities.
- A COA reports purity, identity (mass spec), endotoxin results, and batch number.
- ≥99% purity indicates high-grade research material.
- Third-party verification is more reliable than a vendor testing its own product.