How to Read and Interpret Peptide COA Documents
Master the art of reading Certificates of Analysis. Learn to interpret HPLC results, mass spectrometry data, understand purity percentages, and identify red flags that could indicate quality issues.
What You'll Learn
A Certificate of Analysis (COA) is your primary tool for verifying peptide quality before use in research. Understanding how to read and interpret these documents separates informed researchers from those relying on supplier claims alone.
This guide breaks down every component of a peptide COA, explains the testing methodologies, and teaches you to spot potential quality issues before they affect your research.
What is a Certificate of Analysis?
A COA is an official document from a testing laboratory that verifies:
Identity
Confirms the peptide is what it claims to be through molecular weight verification.
Purity
Measures the percentage of target peptide vs. impurities in the sample.
Quality
Additional tests like endotoxin levels, appearance, and solubility.
Key Components of a COA
- • Product Name: The peptide being tested
- • Batch/Lot Number: Unique identifier for the production batch
- • Molecular Formula: Chemical composition (e.g., C₆₂H₉₈N₁₆O₂₂)
- • Molecular Weight: Theoretical and observed mass
- • Purity (HPLC): Percentage purity from chromatography
- • Mass Spec Results: Molecular weight confirmation
- • Appearance: Physical description (usually white lyophilized powder)
- • Test Date: When analysis was performed
- • Laboratory Information: Who performed the testing
Understanding HPLC Results
HPLC (High-Performance Liquid Chromatography) is the gold standard for measuring peptide purity. Here's how it works:
How HPLC Works
- 1. Sample Injection: A small amount of peptide solution is injected into the HPLC system.
- 2. Separation: The sample passes through a column that separates components based on their chemical properties.
- 3. Detection: A UV detector measures each component as it exits the column.
- 4. Chromatogram: Results appear as peaks on a graph - each peak represents a component.
- 5. Calculation: The main peak (your peptide) is measured as a percentage of total peak area.
Reading the HPLC Chromatogram
- Main Peak: The largest peak represents your target peptide. Its area percentage = purity.
- Retention Time: When the peptide exits the column. Should be consistent for the same peptide.
- Minor Peaks: Small peaks represent impurities (truncated sequences, deletion peptides, etc.).
- Baseline: Should be flat and stable. Noisy baseline can indicate issues.
What to Look For
A legitimate COA should include an actual chromatogram image, not just a purity number. The chromatogram shows a clean, single dominant peak with minimal secondary peaks. Be cautious of COAs that only state "Purity: 99%" without supporting data.
Mass Spectrometry Explained
Mass spectrometry (MS) confirms peptide identity by precisely measuring molecular weight. While HPLC tells you purity, MS tells you "is this actually the peptide I ordered?"
Theoretical Mass
The calculated molecular weight based on the peptide's amino acid sequence. This is the expected value.
Observed Mass
The actual measured molecular weight from the mass spectrometer. Should closely match theoretical mass (within 0.1-1 Da).
Example Mass Spec Results
| Peptide | Theoretical Mass | Observed Mass | Status |
|---|---|---|---|
| BPC-157 | 1419.53 Da | 1419.51 Da | ✓ Match |
| TB-500 | 4963.50 Da | 4963.48 Da | ✓ Match |
| Unknown | 1419.53 Da | 1305.41 Da | ✗ Mismatch |
Peptide Purity Standards
Research Grade (Premium)
Highest quality for demanding research applications. BioInfinity Lab standard.
Research Grade (Standard)
Acceptable for most research applications.
Lower Grade
May be acceptable for some applications. Verify impurity types.
Not Recommended
Too many impurities for reliable research results.
Red Flags to Watch For
No batch/lot number
Every legitimate COA must have a unique batch identifier matching your product.
Generic or template COA
If the COA looks identical for all products or doesn't have specific test dates, it may be fabricated.
No chromatogram images
A number without the actual HPLC trace could be made up. Demand to see the data.
Mass spec mismatch > 1 Da
Large discrepancies between theoretical and observed mass indicate wrong peptide or degradation.
No laboratory information
Legitimate COAs identify who performed the testing. 'In-house' testing without third-party verification is a concern.
Suspiciously round numbers
Exactly '99.00%' purity is unusual. Real results have decimals like '99.23%' or '98.87%'.
Outdated test dates
If the COA is years old, the current batch may not match those results.
Verifying COA Authenticity
Verification Checklist
- Batch number on COA matches the batch number on your product label
- Testing lab is named (third-party verification is ideal)
- Chromatogram images are included, not just purity percentages
- Mass spec shows observed mass within 1 Da of theoretical
- Test date is recent and specific (not just a year)
- Molecular formula matches the peptide ordered
- COA contains specific decimal values, not round numbers
Frequently Asked Questions
What is a Certificate of Analysis (COA)?
A COA is a document from a testing laboratory verifying peptide identity, purity, and quality through analytical methods like HPLC and mass spectrometry.
What purity should I look for?
For research-grade peptides, look for ≥98% minimum. Premium suppliers like BioInfinity Lab provide ≥99% purity peptides.
How do I verify if a COA is legitimate?
Check for batch numbers, chromatogram images, specific test dates, named laboratories, and molecular weight matches. Be wary of generic templates.
What does HPLC purity mean?
HPLC purity indicates the percentage of target peptide vs. impurities. 99% means 99% is your peptide, 1% is synthesis byproducts.
What is mass spectrometry used for?
Mass spec confirms peptide identity by verifying molecular weight matches the expected value. HPLC measures purity; MS confirms identity.
View Our COA Library
Every BioInfinity Lab product comes with a third-party verified COA. Browse our complete library of certificates.