Certificates of Analysis and Purity Testing Methodology
How Peptide Factory verifies batch identity and purity, what a certificate of analysis (COA) contains, and how to request one for your order.
Published April 9, 2026 · Reviewed by Peptide Factory Scientific Team
Why Purity Testing Matters
Synthetic peptides can contain byproducts from incomplete synthesis reactions — truncated sequences, deletion sequences, diastereomers formed during coupling, or residual solvents and counter-ions from purification. For research applications where reproducibility matters, knowing the exact purity and identity of a compound is essential to interpreting experimental results. This is why every batch we manufacture is characterized before release.
Our Testing Methodology
High-Performance Liquid Chromatography (HPLC). Reverse-phase HPLC is the primary method used to determine purity, expressed as the percentage of total peak area attributable to the target compound at a validated wavelength (typically 220 nm or 280 nm, depending on the peptide’s chromophore content). This is the purity figure listed on every product specification table in our catalog.
Mass Spectrometry (MS). Electrospray ionization mass spectrometry (ESI-MS) or matrix-assisted laser desorption/ionization (MALDI-TOF) is used to confirm the molecular weight of the synthesized compound against its theoretical mass, verifying that the correct sequence was synthesized.
Appearance and Solubility Checks. Each lot is visually inspected for consistent physical form (e.g., lyophilized cake appearance) and, where applicable, solubility is checked against standard reconstitution solvents.
What’s in a Certificate of Analysis (COA)
A COA is a batch-specific document that typically includes:
- Product name, lot/batch number, and manufacture date
- HPLC purity result with chromatogram reference
- Mass spectrometry result confirming molecular weight
- Physical appearance and storage recommendation
- Signature/approval from the quality control reviewer
Requesting a COA
Certificates of analysis are available upon request for any batch purchased from Peptide Factory. Bulk and distribution customers can request standing COA documentation as part of their onboarding — see our bulk ordering page for details, or reach out directly via our contact form with your order or lot number.
For a broader overview of our sourcing and quality standards, see Quality Assurance.
This article describes general laboratory testing methodology and does not constitute a guarantee of fitness for any particular research application. Peptide Factory products are supplied for research use only — not for human consumption.
This article describes general research and laboratory information. Peptide Factory products are supplied for research use only — not for human consumption.
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We work directly with licensed distributors and research institutions on bulk supply agreements, documentation packages, and recurring orders.