PeptideChemSF said:The provenance questions are more useful than the numbers.
Thank you for spelling out the reasoning rather than just the conclusion.
Clinical perspective, offered as context rather than as advice.
I tested my certificates of analysis batch through Janoshik — 97.0% purity. That's within acceptable range for compounded peptides. Turnaround was 12 business days.
The test costs ~$123 but gives you actual HPLC chromatography data plus mass spec confirmation. For the peace of mind alone, it's worth every penny. I test every new batch from a new vendor.
PharmHunterJen said:My HPLC chromatogram analysis for certificates of analysis — I sent my batch to Janoshik and here's what the results showed: Main peak retention time:…
Third-party testing services for certificates of analysis besides Janoshik:
Janoshik is the community standard but any ISO-accredited analytical lab can verify peptide identity and purity. The key is independence — don't rely solely on the vendor's own testing.
Community-driven peptide testing and vendor rating platform. Transparent results. Unbiased analysis. Trusted by thousands.
View Resultsamsterdam_pete said:Inter-laboratory variation comes from real methodological differences, not sloppiness: which reference standard was used and how it was itself…
Mass spectrometry confirmation for certificates of analysis: beyond HPLC purity, mass spec tells you the molecule's exact molecular weight. This confirms identity — not just purity.
Why this matters: HPLC can show you a "pure" compound, but if it's pure of the WRONG compound, purity is meaningless. Mass spec at m/z 4113.58 Da confirms it's actually semaglutide. My Janoshik report includes both HPLC and mass spec.
If your testing provider only offers HPLC, consider upgrading to include mass spec for at least your first batch from a new vendor.
Moderator note: a post naming a supplier has been edited. Discuss suppliers in the review sections, not here. Thread quality here is what the rules are for. Keep it up.