How Third-Party COAs Are Generated: Interpreting Peptide Test Results
A practical, research-focused guide to reading Certificates of Analysis (COAs) with a real Vanguard Laboratory example. For laboratory research use only.
A COA (Certificate of Analysis) is a third-party analytical report that documents what was tested, how it was tested, and what the laboratory measured.
At PeptiSearch, we publish COAs so researchers can review identity- and purity-related data directly—without relying on marketing claims.
What a COA Does (and Doesn’t) Tell You
Our Independent Lab Partner: Vanguard Laboratory
PeptiSearch uses Vanguard Laboratory for third-party analytical testing. Vanguard is an independent laboratory that provides
method-based reporting (such as chromatographic analysis). Independence matters: it reduces bias and ensures results come from an external source,
not an in-house report.
A Real Example: MOTS-c COA (Lot MOTSC-1125)
Below is an example of what researchers typically review on a COA: product identification details, the analytical method used, and measured results.
This example corresponds to a specific batch (“lot”) and is published so researchers can evaluate the underlying documentation.
| COA Field | What it means | Why it matters |
|---|---|---|
| Lot / Batch ID | Unique identifier for the tested material | Ensures your COA matches the specific product batch being referenced |
| Method (e.g., HPLC-UV/VIS) | Instrument and detection method used to analyze the sample | Methods determine what can be detected and how results are calculated |
| Purity (Chromatographic) | Percent of signal attributed to the main analyte under the method | A high main peak suggests fewer detectable impurities under that method’s conditions |
| Quantity / Content | Measured amount reported by the lab (method-dependent) | Helps researchers compare “label” vs measured content across lots |
| Uncertainty / Tolerance | Reported uncertainty range (when provided) | Indicates measurement variability within method and lab conditions |
Common COA Misconceptions
These are different measurements and should be interpreted separately.
Why PeptiSearch Publishes Full COAs
- Verification: Researchers can validate lot-specific documentation directly.
- Consistency: COAs provide a repeatable reference point across orders and batches.
- Transparency: We publish the lab’s results as received, without “marketing edits.”
- Long-term: This COA library grows over time as additional lots are tested.
View COAs & Testing Page