Reading a peptide Certificate of Analysis: field by field
Read a published Retatrutide 20 mg COA: sample reference, area purity, measured content, fill accuracy and the limits of the reported tests.
A certificate of analysis describes the sample tested and the measurements performed. Start with the reference and vial size, then read each result alongside its method. A purity percentage alone does not describe every property of the material.
A real example: Retatrutide 20 mg
This walkthrough uses report CPT-RETA-20-091226, version 7, issued by Canada Peptide Testing on September 12, 2026. Open the complete PDF or its laboratory verification record alongside this explanation.
| Report field | Reported value | Meaning |
|---|---|---|
| Lot number | PNP-RTT-2706 | Client-declared reference for the submitted sample. |
| Method | RP-HPLC-UV, 220 nm | Analytical method and detection wavelength. |
| Area purity | 99.31% | Reported chromatographic area percentage under that method. |
| Expected content | 20.00 mg | The client-declared label claim. |
| Measured content | 20.24 mg | Content calibrated against the laboratory's working standard. |
| Fill accuracy | 101.2% | 20.24 divided by 20.00, multiplied by 100. |
Purity and content are separate measurements
The report gives both 99.31% area purity and 20.24 mg measured content. Its content calculation is on an as-received basis, uncorrected for water and counter-ion content. Keep that qualification when comparing reports. A theoretical molecular mass printed in the sample description is not an observed mass-spectrum result.
Read the limits of the report
This report contains HPLC-UV area purity and content results. It does not report mass-spectrometric identity confirmation, sterility, endotoxin or water-content testing. An omitted test is not a passing result. The conformity statement applies to the stated area-purity specification of at least 98.0%, and results apply to the sample tested.
Match the report before ordering
Check the Retatrutide product page for the selected size and certificate. This 20 mg report does not establish results for a 10 mg vial or another lot. Some other published reports use an assigned reference that differs from the photographed vial code. Request the documented sample-to-lot mapping before treating those references as a match.
Keep with your sample records
- The full PDF, report number and version.
- The product size and lot or assigned reference.
- The laboratory verification link and reporting statements.
- Any documented explanation connecting the tested sample to your supplied lot.
Pure North publishes laboratory reports for the samples and vial sizes listed in Lab Results. Each report identifies its method, reference, area purity and measured content. Open the matching product page to check coverage for the size you select. A report does not cover every size or future lot; contact customer service if your vial reference differs. Bacteriostatic water has no COA.
Frequently asked questions
What specification does this report use?
The example report states at least 98.0% area purity. Its 99.31% result meets that specification; the conformity statement does not extend to untested properties.
Why does net peptide content matter?
It tells you what fraction of the vial weight is actual peptide vs counter-ion and water. For stoichiometric experiments, 80% net peptide vs 60% changes your effective concentration meaningfully.
What is a 'lot-specific' COA?
A COA tied to one specific synthesis batch with the lot number from your order confirmation. A 'per-product' generic COA is not lot-specific and is a red flag.
Should I trust the supplier's own COA?
Trust but verify. An accredited independent retest gives a stronger signal than a manufacturer's own QC certificate alone.
Where can I see Pure North's COAs?
Open Lab Results or the matching product page. For help matching an assigned reference, see our reference-verification guide.
Disclaimer: All Pure North Peptides products are supplied for laboratory research use only. They are not approved by Health Canada as drugs. See our research-use declaration for full terms.
For laboratory research use only. Reference information, not medical advice or human-use guidance.
