Peptide education
How to Read a Certificate of Analysis (CoA)
A Certificate of Analysis (CoA) summarizes key identity and purity results for a specific lot. Use this guide to verify what you received, understand common test methods, and compare documentation across products.
CoA fundamentals
What a CoA Should Include
While formats vary by lab, a complete CoA should make it easy to trace the sample, confirm the analyte identity, and interpret the reported purity and quantity.
Product & lot traceability
Look for the product name, lot/batch number, and (when provided) a unique sample ID. These identifiers should match your product label and order details.
Test methods & instruments
A credible CoA lists the analytical method(s) used (e.g., HPLC/UPLC, LC-MS) and may include instrument or SOP references so results can be reproduced.
Results & acceptance criteria
Results should be clearly labeled with units (%, mg/vial, etc.). If specifications are listed, they should be stated as ranges or thresholds (e.g., purity ≥ 98%).
Dates, signatures & lab details
Check the test date, report date, and the issuing laboratory’s name/contact. Many labs include an analyst/reviewer sign-off or digital verification.
Interpreting results
Key CoA Sections Explained
Most peptide CoAs present a short summary followed by analytical data. Focus on the sections below to understand what was tested and how to compare lots. Identity: Often supported by mass spectrometry (MS) data that aligns with the expected molecular weight. Purity: Commonly reported from HPLC/UPLC as a percentage based on peak area integration. Quantity: May be stated as net peptide content (mg) and can be supported by gravimetric or quantitative methods. Appearance & storage: Notes such as “white lyophilized powder” and recommended storage conditions help with handling and stability.
Common Test Types You May See
Not every report includes every test. The methods below are commonly used to support identity and purity claims for research peptides.
HPLC / UPLC purity
Chromatography separates components; purity is typically reported as % area of the main peak.
LC-MS identity
Mass spectrometry supports identity by matching observed mass/charge to the expected peptide mass.
Peptide content (mg)
Reported net content may be based on fill weight and/or quantitative methods; confirm units and basis.
Residual solvents
Some labs report residual solvents from synthesis/purification to support handling and quality documentation.
Water content
Moisture can affect handling and stability; Karl Fischer titration is a common method when reported.
Counterion / salt form
Reports may specify acetate/TFA or other counterions; salt form can affect mass and calculations.
CoA FAQs
Quick answers to common questions about interpreting and comparing Certificates of Analysis.
Does a higher purity percentage always mean “better”?
Not necessarily. Purity is one quality indicator, but context matters (method, integration settings, and what impurities are present). Compare like-for-like methods and ensure units and criteria are clearly stated.
Why can two CoAs for the same peptide look different?
Labs use different templates, instruments, columns, gradients, and reporting conventions. Focus on traceability (lot/sample ID), method type, and clearly labeled results rather than formatting.
What is “% area” on an HPLC report?
It typically refers to the proportion of the main chromatographic peak area relative to total integrated peak area. It is a common way to report purity, but it depends on how peaks are integrated and detected.
What should match between my product label and the CoA?
At minimum: product name and lot/batch number. If a sample ID is provided, it should correspond to the tested lot. Dates and lab identifiers help establish documentation integrity.
Can I use a CoA to confirm sterility or endotoxin levels?
Only if those tests are explicitly listed. Standard peptide CoAs often focus on identity and purity; sterility/endotoxin require separate validated assays and will be stated as such when performed.
Where can I find the CoA for my order?
If your product listing includes a CoA link, you can access it there. If you need help locating documentation for a specific lot, contact our team with your order number and lot number.
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Choose research peptides with clear documentation
Browse our catalog and look for lot-specific documentation where available. If you have questions about a CoA or test method, contact us before you purchase.