What is a Certificate of Analysis?
A Certificate of Analysis (COA) is a quality document that accompanies research compounds, providing detailed analytical data about the product's identity, purity, and specifications. Understanding how to read a COA is essential for evaluating the quality of materials before use in your research.
This guide walks through each section of a typical COA and explains what the data means for researchers.
Essential COA Components
Product Identification
The header section should clearly identify:
- Product Name: The compound name or common identifier
- CAS Number: Chemical Abstracts Service registry number for compound identification
- Molecular Formula: The elemental composition (e.g., C45H66N12O12S2)
- Molecular Weight: Theoretical mass in Daltons
- Sequence: For peptides, the amino acid sequence
- Batch/Lot Number: Unique identifier for traceability
Testing Laboratory Information
A legitimate COA should identify:
- Laboratory name and contact information
- Accreditation details (ISO 17025, GLP, etc.)
- Date of analysis
- Analyst identification or signature
Third-party COAs are particularly valuable as they provide unbiased verification. Learn more about the importance of third-party testing.
Understanding HPLC Results
Purity Percentage
The HPLC purity percentage indicates the proportion of your target compound relative to all detected materials:
- ≥99%: Highest purity, suitable for sensitive assays and validation studies
- 97-99%: High purity, appropriate for most research applications
- 95-97%: Standard research grade, suitable for screening and preliminary studies
- <95%: May require additional purification for sensitive applications
The Chromatogram
The HPLC chromatogram is a visual representation of the separation:
- Main Peak: Should be dominant, representing your target compound
- Retention Time: The time at which the compound elutes from the column
- Peak Area: Proportional to the amount of compound (used to calculate purity)
- Minor Peaks: Represent impurities—smaller is better
Method Details
A complete COA should specify the HPLC method:
- Column Type: Usually C18 reverse-phase for peptides
- Mobile Phase: The solvent system used
- Flow Rate: Affects separation and retention times
- Detection Wavelength: Typically 214-220 nm for peptides
- Gradient Program: How solvent composition changes over time
Understanding Mass Spectrometry Results
Observed vs. Theoretical Mass
Mass spectrometry confirms compound identity:
- Theoretical Mass: The calculated molecular weight based on the structure
- Observed Mass: The measured molecular weight
- Mass Accuracy: Typically should be within ±0.1% of theoretical
Reading the Mass Spectrum
Key features to look for:
- [M+H]+: The singly protonated molecular ion (most common)
- [M+2H]2+: Doubly charged ion (common for larger peptides)
- [M+Na]+: Sodium adduct (can appear in some samples)
- Charge State Distribution: Pattern of multiply charged ions
Ionization Method
Common ionization methods for peptides:
- ESI (Electrospray Ionization): Most common for peptides, produces multiply charged ions
- MALDI (Matrix-Assisted Laser Desorption/Ionization): Produces singly charged ions, good for larger peptides
Additional Quality Parameters
Appearance
Physical description of the product:
- Color (typically white to off-white for lyophilized peptides)
- Form (powder, lyophilized cake, crystals)
- Any notable characteristics
Solubility
Information about how the compound dissolves:
- Recommended solvents
- Concentration limits
- Special considerations
Water Content
For lyophilized products, water content (often measured by Karl Fischer titration) indicates:
- Degree of desiccation
- Storage stability expectations
- Actual peptide content (important for precise weighing)
Peptide Content
The net peptide content accounts for:
- Water content
- Counter-ion content (e.g., TFA, acetate salts)
- Actual active compound weight
For accurate dosing, use the peptide content percentage to calculate the actual amount of compound.
Red Flags to Watch For
Be cautious if a COA:
- Lacks laboratory identification or accreditation information
- Has no batch/lot number for traceability
- Missing chromatogram or mass spectrum
- Shows inconsistencies between stated and measured values
- Has no date or analyst identification
- Uses generic or copied data not specific to the batch
Requesting Additional Information
Don't hesitate to request:
- Full chromatograms if only summaries are provided
- Raw data files for verification
- Repeat analyses if results seem questionable
- Historical batch data for consistency assessment
- Extended impurity profiles
Documentation for Your Records
Good laboratory practice includes:
- Retaining COAs with your research records
- Linking COA data to experimental notebooks
- Including COA references in publications
- Maintaining lot-specific records for reproducibility
For more on documentation best practices, see our Documentation Standards guide.
Our COA Standards
All Maple Research Labs products include comprehensive COAs featuring:
- Third-party testing from accredited laboratories
- Complete HPLC and MS data with chromatograms
- Batch-specific testing for every lot
- Full traceability documentation
Visit our Lab Standards page to learn more about our quality assurance processes.
Conclusion
A well-prepared Certificate of Analysis is your primary tool for evaluating research compound quality. By understanding how to read and interpret these documents, you can make informed decisions about the materials you use and ensure the integrity of your research.
Have questions about interpreting a specific COA? Contact our team for assistance.