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Purity Claims vs Analytical Verification: What Third-Party Testing Actually Reveals
When a supplier lists '99% purity' without specifying the analytical method, assume the number refers to crude purity (total peptide content relative to non-peptide material like salts and buffers) rather than sequence purity (percentage of full-length, correc
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- When a supplier lists '99% purity' without specifying the analytical method, assume the number refers to crude purity (total peptide content relative to non-peptide material like salts and buffers) rather than sequence purity (percentage of full-length, correctly sequenced tesamorelin). Crude purity can reach 98–99% even when 5–10% of the peptide content consists of truncated sequences, deletion analogues, or oxidised variants. HPLC purity. The percentage of the sample that elutes as a single peak at the expected retention time. Is a more meaningful metric, but even HPLC can't differentiate peptides with identical hydrophobicity but different sequences.
- Real Peptides provides both HPLC chromatograms (showing >98% peak purity) and MALDI-TOF mass spectra (confirming molecular weight within ±1 Da of theoretical) for every batch. Competitors who publish certificates of analysis typically show HPLC data only. And even then, the COA often comes from the raw material supplier in China rather than independent U.S. or European testing labs. The practical difference: a COA from the manufacturing facility has no third-party accountability, whereas independent lab verification (Real Peptides uses ISO 17025-accredited labs) provides enforceable quality standards. Endotoxin contamination is the silent failure mode most tesamorelin buyers never check. Bacterial endotoxins. Lipopolysaccharide fragments from E. coli used in recombinant peptide production. Trigger inflammatory responses in cell cultures and animal models even at concentrations below 1 EU/mg (endotoxin unit per milligram). Real Peptides tests every batch using LAL (Limulus amebocyte lys