A Certificate of Analysis (COA) is a document from a testing laboratory that verifies the identity, purity, and quality of a peptide product. It is the single most important quality indicator available to researchers. If a supplier cannot provide a COA for a specific batch, that is a major red flag.
Key Sections of a Peptide COA
1. Product Identification
This section lists:
- Peptide name and sequence: The amino acid sequence should match the intended compound
- Molecular weight: The calculated molecular weight for the sequence
- Batch/lot number: A unique identifier for this specific production batch
- Quantity: Amount in the vial
2. HPLC Purity
This is the most important number on the COA. High-Performance Liquid Chromatography (HPLC) separates the peptide from impurities and measures what percentage of the total material is the target compound.
| HPLC Purity | Quality Level | Suitability |
|---|---|---|
| 99%+ | Exceptional | Premium research grade |
| 98-99% | High | Standard research grade — most common |
| 95-98% | Acceptable | Usable but not ideal |
| Below 95% | Low | Not recommended for injection research |
A good COA includes the actual HPLC chromatogram — the graph showing the separation. Look for a single dominant peak (the target peptide) with minimal secondary peaks (impurities).
3. Mass Spectrometry (MS)
Mass spectrometry confirms the identity of the peptide. The observed molecular weight should match the theoretical molecular weight within an acceptable tolerance (typically ±1 dalton). This confirms you actually have the peptide you ordered, not a different compound or a truncated version.
4. Appearance
Should state "white to off-white lyophilized powder" for most peptides. Any unusual color descriptions may indicate impurities or degradation.
5. Endotoxin Testing (if included)
Endotoxins are bacterial cell wall fragments that can cause fever, inflammation, and adverse reactions if injected. A quality COA for injectable research peptides should include endotoxin testing results, typically measured in EU/mg (Endotoxin Units per milligram). Acceptable levels are generally below 5 EU/mg for research use.
6. Sterility Testing (if included)
Not all COAs include sterility data, but premium-grade peptides may show sterility testing results confirming no bacterial or fungal contamination.
Red Flags on a COA
- No HPLC chromatogram included — just a number without the supporting graph
- Purity below 95% — especially for injection research
- MS molecular weight doesn't match — wrong product or degraded
- Generic or template COA — not batch-specific, with no lot number
- No lab name or contact information — legitimate labs identify themselves
- Dates that don't match — testing date should be close to or before the sale date
- Suspiciously perfect numbers — a COA showing exactly 99.99% on every test may be fabricated
Third-Party vs In-House Testing
| Aspect | In-House Testing | Third-Party Testing |
|---|---|---|
| Independence | Potential bias — tested by the seller | Independent verification |
| Reliability | Variable | Generally higher |
| Cost | Lower (included in production) | Higher (additional expense) |
| Trust level | Moderate | High |
The gold standard is third-party testing — an independent lab with no financial relationship to the supplier. Some reputable third-party labs include Janoshik Analytical, Colmaric Analyticals, and various university analytical chemistry departments.
Should every peptide I buy come with a COA?
Yes. Any reputable supplier provides batch-specific COAs for every product. If a supplier cannot or will not provide a COA upon request, consider this a serious red flag and look elsewhere. The COA should be specific to your batch (matching lot number), not a generic document.
Can COAs be faked?
Unfortunately, yes. This is why third-party testing is valuable. Signs of a fake COA include generic templates, impossibly perfect numbers, no lab contact information, and COAs that look identical across different batches. Some researchers send samples for independent third-party verification when trying a new supplier for the first time.