What Is a Certificate of Analysis?
A Certificate of Analysis (COA) is a document issued by an independent laboratory that summarizes the test results for a specific batch of product. It serves as proof that the product meets stated quality specifications. For context on the testing methods that generate these results — HPLC and mass spectrometry — see Lab Testing & Verified Purity.
Key Sections of a COA
Product Information
- Product Name: The peptide being tested
- Batch/Lot Number: A unique identifier for the specific production batch
- Quantity: The amount of peptide in the vial
- Date of Analysis: When the testing was performed
HPLC Purity
This is the most important metric. HPLC (High-Performance Liquid Chromatography) separates the components of a sample and measures the percentage that is the target peptide.
- How to read it: Look for "Purity by HPLC" or "HPLC Purity." A result of 99.4% means 99.4% of the sample is the intended peptide.
- What to expect: Phase 1 Peptides targets 99%+ purity for all products.
For a full walkthrough of HPLC chromatogram anatomy, peak area normalization, and impurity peak interpretation, see How to Read HPLC Purity Data.
Mass Spectrometry (MS)
Mass spectrometry confirms the molecular identity of the peptide by measuring its molecular weight.
- How to read it: The "Observed MW" should closely match the "Theoretical MW" listed. A match within 1 dalton confirms correct identity.
- Why it matters: This ensures the peptide has the correct amino acid sequence and has not been misidentified or contaminated.
Net Peptide Content
This measures the weight percentage of actual peptide in the lyophilized powder, accounting for water, salts, and counterions (like acetate or TFA).
- Typical range: 60–85% for most lyophilized peptides
- Why it matters: If a vial contains 10mg of powder with 75% net peptide content, you have 7.5mg of active peptide. This is critical for accurate concentration calculations in experiments. For the formulas and worked examples needed to convert net peptide content into accurate stock concentrations, see the Peptide Concentration Calculations guide.
The primary reason net peptide content is below 100% is the presence of TFA (trifluoroacetate) counterion from HPLC purification. For a full explanation of how TFA enters the compound during synthesis and what it means for purity reporting, see TFA Content in Research Peptides.
Appearance
Describes the physical form of the product. Research peptides are almost universally supplied as lyophilized (freeze-dried) powder — see Lyophilization & Freeze-Drying for why this form is used and what it means for reconstitution and storage. (typically "white to off-white lyophilized powder").
Solubility
Notes the recommended solvents and expected solubility, which is important for reconstitution.
How to Verify Your COA
1. Check the batch number on the COA matches the label on your vial
2. Confirm the molecular weight is within range of the theoretical value
3. Verify purity meets or exceeds the stated specification
4. Review any additional tests (e.g., net peptide content) that may be listed for your specific compound
Questions?
What should a researcher verify first when reviewing a research peptide COA?Start by confirming the batch or lot number on the COA matches the vial label — this ensures the analytical data applies to the specific material you received. Then verify the HPLC purity meets the stated specification, confirm the observed molecular weight from mass spectrometry matches the theoretical value within ±1 dalton, and check that the date of analysis is within the last 24 months.
What is the difference between an in-house and a third-party COA?A third-party COA is issued by an independent laboratory that has no financial relationship with the product supplier. An in-house COA is generated by the supplier's own lab. Third-party COAs carry higher credibility because the testing laboratory has no commercial incentive to report favorable results. Phase 1 Peptides publishes third-party batch-level COAs so researchers can review independently generated analytical data.
Why does net peptide content matter for laboratory research?Net peptide content measures the actual peptide mass per unit weight of lyophilized powder, after accounting for water, salts, and counterions. A vial with 10 mg of powder at 75% net peptide content contains approximately 7.5 mg of active peptide. Ignoring net peptide content in concentration calculations produces systematically inaccurate stock concentrations, which propagates errors through every downstream experiment that uses that stock.
What does the "Theoretical MW" vs "Observed MW" comparison on a COA confirm?The theoretical molecular weight is calculated from the known amino acid sequence of the peptide. The observed MW is the measurement from mass spectrometry. A match within ±1 dalton confirms the compound has the correct chemical identity — the right amino acid sequence, modifications, and structure. A significant mismatch is a red flag indicating either a wrong compound or a synthesis error.
If you have questions about a specific COA or need additional testing data, contact our support team at support@phase1-peptides.com. For a more detailed walkthrough of reading and verifying COA data, see How to Verify a Research Peptide COA. Batch-level test records are published on the Lab Tests page. For a dedicated walkthrough of how the LC-MS identity data on a COA is generated and interpreted, see LC-MS Identity Confirmation. For a comparison of how HPLC and LC-MS work together in research peptide documentation, see HPLC vs LC-MS: A Researcher's Comparison. For storage requirements after reconstitution, see Storage & Handling Best Practices. For a structured checklist approach to reviewing the fields on a COA, see the Peptide COA Review Checklist.