Peptide Certificate of Analysis (COA) documents can be dense: chromatograms, molecular weights, retention times, lot identifiers, and test-method notes may all appear on one report.
This research-use-only guide explains how to review those fields without treating a purity percentage as proof of identity. You can also compare Mytide Lab's currently published, lot-specific documents on the peptide COA and lab reports page. Products still awaiting documentation are marked pending there instead of being presented as COA-backed.
What Is a COA?
A Certificate of Analysis is a document that reports the results of quality testing performed on a specific batch of peptide. It typically includes:
- Identity confirmation (is this actually the peptide you ordered?)
- Purity measurement (how much of the sample is the target peptide?)
- Physical characteristics (appearance, solubility)
- Batch-specific information (lot number, manufacturing date)
Think of it as a peptide's report card. And just like report cards, you need to know what the grades mean.
Section 1: Product Identification
At the top of any COA, you'll find basic identification information:
- Product name - The peptide name (e.g., BPC-157, TB-500)
- Catalog/Product number - Supplier's internal reference
- Lot/Batch number - Unique identifier for this specific production batch
- Molecular formula - The chemical formula (e.g., C₆₂H₉₈N₁₆O₂₂ for BPC-157)
- Molecular weight - Expected mass in Daltons
- Sequence - The amino acid sequence of the peptide
- Quantity - How much peptide is in the vial
What to check: Make sure the sequence and molecular weight match the peptide you ordered. This sounds basic, but it's your first line of defense against receiving the wrong compound.
Section 2: HPLC Purity - One Part of the Evidence
HPLC (High-Performance Liquid Chromatography) can estimate the relative purity of components detected under the stated method. It does not, by itself, establish that the main peak is the intended compound. Review HPLC alongside identity data, the reported method, and the lot number.
How HPLC Works
The peptide sample is dissolved and pushed through a column packed with tiny particles. Different molecules travel through the column at different speeds based on their size and chemical properties. A detector at the end measures what comes out and when.
The result is a chromatogram - a graph showing peaks at different retention times. The main peak represents your target peptide. Any smaller peaks represent impurities.
What the Numbers Mean
An HPLC percentage is method- and sample-specific. Read the reported value directly from the lot-specific document and check whether the report includes a chromatogram, integration table, test date, sample identifier, and laboratory name. Do not substitute a catalog-wide average or product-page specification for the result on the report tied to the material being reviewed.
Reading the Chromatogram
If the COA includes the actual HPLC chromatogram graph, here's what to look for:
- One dominant peak - Your target peptide. It should tower over everything else.
- Clean baseline - The flat line between peaks should be relatively smooth, not jagged or elevated.
- Minimal secondary peaks - Small peaks indicate impurities. They should be tiny relative to the main peak.
- Retention time - Where on the x-axis the main peak appears. This should match the expected retention time for your peptide.
Common HPLC Impurities
- Deletion sequences - Peptides missing one or more amino acids from the synthesis
- Truncated sequences - Incomplete peptide chains
- Oxidation products - Especially common for peptides containing methionine or cysteine
- Racemization products - Amino acids in the wrong stereochemical configuration
- TFA salts - Residual trifluoroacetic acid from purification (usually listed separately)
Section 3: Mass Spectrometry (MS)
Mass spectrometry confirms that the peptide has the correct molecular weight - essentially proving you have the right compound.
How It Works
The peptide is ionized and sent through a mass analyzer that separates molecules by their mass-to-charge ratio (m/z). The result shows the observed molecular weight, which should match the theoretical molecular weight.
What to Look For
- Observed mass vs. theoretical mass - These should match within ±1 Da (Dalton) for most peptide MS methods
- ESI-MS or MALDI-TOF - The two most common MS methods for peptides. Both are reliable.
- m/z values - You may see multiple values representing different charge states (e.g., [M+H]⁺, [M+2H]²⁺). This is normal.
Example
Compare the observed ions and charge-state interpretation with the theoretical mass stated for the compound. The acceptable tolerance depends on the instrument, ionization method, calibration, adducts, and report method, so a universal pass/fail cutoff should not replace the laboratory's stated criteria.
Section 4: Appearance and Physical Properties
This section describes what the peptide looks like and how it behaves:
- Appearance - Usually "white to off-white lyophilized powder." Yellow or brown color can indicate degradation.
- Solubility - States which solvents the peptide dissolves in (typically water, BAC water, DMSO, or dilute acetic acid)
- pH - The pH of a solution at a specified concentration
These might seem minor, but they're useful for confirming you received what you expected and for troubleshooting reconstitution issues.
Section 5: Additional Tests
Some COAs include extra quality tests:
Amino Acid Analysis (AAA)
Breaks down the peptide into individual amino acids and measures the ratio of each. This confirms the peptide composition matches the expected sequence. It's particularly valuable for longer peptides where sequence accuracy is critical.
Peptide Content
This tells you what percentage of the vial's total weight is actually peptide (as opposed to water, salts, and counterions). Peptide content is typically 60-85% by weight.
Important: Peptide content is not the same measurement as HPLC purity. Water, counterions, salts, and other components may affect total mass. Their relevance depends on the material and experimental design, so review the actual report rather than assuming they are immaterial.
Endotoxin Testing (LAL)
Measures bacterial endotoxin levels. Important for in vivo research applications. Results are typically reported in EU/mg (Endotoxin Units per milligram).
Sterility Testing
Confirms the absence of microbial contamination. Not all suppliers include this, but it's valuable for sensitive research protocols.
Red Flags: When to Question a COA
Here are warning signs that a COA might not be trustworthy:
1. No Lot Number
Every COA should reference a specific batch. A generic COA without a lot number suggests the document may not represent the actual product you received.
2. Perfect Round Numbers
If every measurement is suspiciously round (exactly 99.0%, exactly 1,419.0 Da), it may be a template rather than actual test results. Real analytical data has decimal places and slight variations.
3. Missing Chromatogram
The best COAs include the actual HPLC chromatogram graph - not just a number. If a supplier only provides a purity percentage without supporting data, ask for the full chromatogram.
4. No MS Data
HPLC purity alone does not establish identity. Look for an orthogonal identity method, such as mass spectrometry, and verify that the sample or lot identifier matches the rest of the documentation.
5. Unrealistic Purity Claims
If every single product in a catalog claims 99.9%+ purity, be skeptical. Peptide synthesis has inherent limitations, and while high-purity synthesis is achievable, claiming near-perfect purity across all products suggests the numbers may not be real.
6. Third-Party vs. In-House Testing
Independent testing can provide useful separation between seller and laboratory, but it still requires basic verification: laboratory identity, report date, lot match, method details, and an unaltered report file.
How to Use COA Data in Your Research
For Publication
If you're publishing research, include the peptide supplier, catalog number, lot number, and purity in your methods section. Reviewers and readers need to know the quality of materials used.
For Troubleshooting
If you're getting unexpected results, the COA is your first diagnostic tool:
- Low purity could explain inconsistent dose-response curves
- Wrong molecular weight means you might have the wrong compound
- High counterion content (low peptide content) means your actual peptide mass is less than the total weight
For Comparing Suppliers
COAs let you objectively compare peptide quality between suppliers. When evaluating a new source, request COAs for several products and check them against the criteria above.
Mytide Lab COA Standards
Mytide Lab separates published documentation from pending records on the lab reports page. Downloadable reports are currently shown for GHK-Cu, PT-141, Retatrutide, Tirzepatide, NAD+, and Wolverine Blend. Each published entry displays its reported lot, laboratory, purity value, and available report files. A product marked pending should not be interpreted as having a completed, product-specific COA.
Match the lot on the downloadable report to the material under review. For a report that is not published, contact Mytide Lab with the product and lot identifier rather than relying on a general purity statement.
Quick Reference: COA Checklist
Use this checklist when reviewing any peptide COA:
- ✅ Lot/batch number present
- ✅ HPLC result and chromatogram are tied to the same sample or lot
- ✅ Mass spectrometry interpretation is consistent with the stated method and theoretical mass
- ✅ Amino acid sequence listed and correct
- ✅ Physical appearance described
- ✅ Peptide content percentage stated
- ✅ Date of analysis
- ✅ Testing laboratory identified
If key identity, lot, method, or laboratory details are missing, ask for more complete documentation before using the material in a research workflow.
This page is educational and intended only for laboratory research sourcing and documentation review. Mytide Lab products are not for human consumption, medical use, or therapeutic application.
