Understand the source comparison
P21 Real vs Fake: Visual and Lab Comparison
Lyophilised appearance Compact white-to-off-white cake, evenly distributed at vial bottom Scattered powder, chalky residue on vial walls, or friable dust-like texture Visual inspection under bright light Authentic lyophilisation produces a cohesive cake; scatt
No winner is assigned.
This page preserves a source comparison for education. It does not add a rating, recommendation or clinical judgment.
- Lyophilised appearance
- Compact white-to-off-white cake, evenly distributed at vial bottom
- Scattered powder, chalky residue on vial walls, or friable dust-like texture
- Visual inspection under bright light
- Authentic lyophilisation produces a cohesive cake; scattered powder indicates improper freeze-drying or no vacuum process
- Reconstitution behaviour
- Dissolves completely in 60–90 seconds, crystal-clear colourless solution, no particles
- Cloudiness, precipitate formation, gelatinous clumps, or incomplete dissolution
- Add 1mL bacteriostatic water, observe without shaking
- Cloudiness or clumping is immediate disqualification; authentic P21 reconstitutes uniformly with gentle swirling
- HPLC purity
- Single dominant peak at expected retention time, ≥98% purity
- Multiple peaks, off-target retention time, or no detectable peptide signal
- Third-party HPLC analysis (Colmaric, Janoshik)
- HPLC separates authentic synthesis from fragment contamination or wrong compounds; <98% purity indicates synthesis failure
- Mass spectrometry
- Molecular weight 1682.95 Da ±0.5 Da
- Mass >50 Da off target, or no peptide mass detected
- Mass spec confirmation via independent lab
- Confirms molecular identity; off-target mass means it's not P21 regardless of labeling
- Endotoxin level
- <1.0 EU/mg (pharmaceutical-grade threshold)
- Often >10 EU/mg, indicating bacterial contamination
- LAL assay (limulus amebocyte lysate test)
- Endotoxin >1 EU/mg compromises research validity and signals non-sterile production environments
- Batch traceability
- CoA with batch number matching vial label, synthesis date, stability data
- Generic CoA with no batch reference, or no CoA provided
- Request batch-specific CoA before purchase
- Batch traceability is mandatory for pharmaceutical-grade peptides; absence indicates unverified sourcing