What a Peptide CoA Should Contain
A complete Certificate of Analysis for pharmaceutical-grade peptide API should include: product identification (name, sequence, CAS number), lot number and manufacturing date, the testing laboratory name and accreditation, HPLC purity analysis, mass spectrometry data, endotoxin test results, residual solvent analysis, appearance, and release authorization. Any CoA missing more than one of these sections should prompt a request for the complete documentation before accepting the lot.
Section 1: Product Identification
The top of the CoA should clearly state the product name, amino acid sequence, molecular formula, molecular weight, and CAS number. Verify that the CAS number matches the peptide you ordered — there are known cases of mislabeled products where the CAS number corresponds to a different compound. Cross-reference the CAS number at a public chemical database (PubChem, ChemSpider) before accepting a new supplier's documentation.
The lot number should be unique and present on both the CoA and the physical container label. Mismatches between the CoA lot number and the container label are a significant red flag indicating either a documentation error or intentional mislabeling.
Section 2: HPLC Purity Analysis
High-performance liquid chromatography (HPLC) is the primary method for determining peptide purity. The CoA should show:
- The chromatogram itself — not just a purity percentage. A chromatogram shows the individual peaks for the main product and all impurities, with integration values. A single number without a chromatogram cannot be verified.
- The integration report — showing the area percentage for each peak. The main peptide peak should constitute ≥99% of total peak area for pharmaceutical-grade material.
- Column and mobile phase conditions — allowing the analysis to be replicated if needed. Legitimate analytical reports include method parameters.
- Detection wavelength — typically 220nm for peptide bond detection or 215nm for UV-absorbing peptides.
What to look for: Multiple small peaks adjacent to the main peak may indicate synthesis truncation products or dimerization. A main peak below 98% area percentage is a rejection criterion for most compounding applications. An unusually "clean" chromatogram with no visible impurity peaks whatsoever may indicate a manipulated or fabricated document.
Section 3: Mass Spectrometry (MS) Confirmation
Mass spectrometry confirms the identity of the peptide by verifying its molecular weight. For peptides, the CoA should report the observed mass versus the theoretical mass, typically as:
- The molecular ion [M+H]⁺ (protonated molecular ion)
- Multiply charged ions [M+2H]²⁺, [M+3H]³⁺ for larger peptides
- Theoretical MW of the peptide
- Observed MW with mass accuracy (typically ±0.5 Da for standard instruments, ±5 ppm for high-resolution instruments)
If the observed mass does not match the theoretical mass within acceptable tolerance, the material may be a different peptide, a truncated synthesis product, or may have undergone oxidation or other degradation. Always verify the theoretical MW of the peptide using its amino acid sequence and a peptide mass calculator before reviewing MS data.
Section 4: Endotoxin Testing
For peptide API intended for injectable compounding, endotoxin testing is non-negotiable. The standard test method is the LAL (Limulus Amebocyte Lysate) assay. The CoA should state:
- Test method: LAL (gel clot, turbidimetric, or chromogenic)
- Specification limit: typically <1 EU/mg for injectable peptide API
- Lot result: the actual endotoxin level measured for this specific lot
- Test date
A CoA that says "endotoxin: pass" without reporting the actual measured value is incomplete. Request the actual result. Endotoxin levels well below the specification limit (<0.1 EU/mg) indicate well-controlled manufacturing; results at or near the limit warrant closer evaluation.
Section 5: Residual Solvents
Solid-phase peptide synthesis uses organic solvents including DMF (dimethylformamide), DCM (dichloromethane), acetonitrile, and methanol. Residual solvent analysis per ICH Q3C guidelines classifies solvents by risk: Class 1 (avoid), Class 2 (limit), and Class 3 (low toxic potential). The CoA should confirm that residual levels are within ICH Q3C limits. DMF and DCM are Class 2 solvents with daily exposure limits — their residual levels should be confirmed as below specification for every lot.
Section 6: Appearance
Most peptide API appears as a white to off-white lyophilized powder. The CoA should specify the appearance and it should match your physical inspection of the material. Yellow or brown discoloration may indicate oxidation, degradation, or impurities. A significant mismatch between the CoA appearance description and the actual material warrants refusal of the lot.
Frequently Asked Questions
What is the minimum acceptable HPLC purity for peptide API?
≥99% for standard therapeutic peptides. ≥98% for complex molecules. Below 97% is generally not acceptable for injectable compounding.
What endotoxin level is acceptable for injectable peptides?
<1 EU/mg by LAL test. The CoA should state both the specification limit and the actual lot result — not just "pass."
What should I do if a CoA does not include endotoxin data?
Do not accept the lot for injectable use. Request testing before shipment. If the supplier cannot provide endotoxin data, source from a supplier who can.