Purity Visual Guide
Learn to evaluate peptide quality by appearance. Reference these criteria when inspecting lyophilized powders and reconstituted solutions.
Excellent
- Clear, colorless solution after reconstitution with no visible particulates
- Lyophilized powder is a uniform white puck with no discoloration
- HPLC purity >98% confirmed by third-party lab
- Mass spec results match expected molecular weight within 0.1%
- Endotoxin levels <0.25 EU/ml
Acceptable
- Solution is clear with very slight opalescence
- Powder is white to off-white with minor fragmentation
- HPLC purity 95-98% with identified minor impurity peaks
- Mass spec within 0.5% of expected molecular weight
- COA provided by vendor matches claimed specifications
Concerning
- Visible particulates or turbidity after reconstitution
- Yellow or brown discoloration of lyophilized powder
- HPLC purity 90-95% or major unidentified peaks present
- COA appears templated with no specific lot data
- Reconstituted solution develops cloudiness over 24 hours
Reject
- Gel-like or clumped residue that does not dissolve
- Strong odor or unusual color (dark yellow, brown, green)
- HPLC purity <90% or no COA provided
- Vial seal is compromised, crimped poorly, or shows signs of tampering
- Mass spec shows completely wrong molecular weight
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