Dr.PulmRoch said:I tested my certificates of analysis batch through Janoshik — 97.3% purity.
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: 14.8 minutes (consistent with semaglutide reference standard)
Peak purity: 98.0%
Related substances: 0.8% (single impurity at 8.4 minutes — likely a synthesis intermediate)
Mass spec: m/z 4113.58 (matches expected molecular weight)
This is a clean result. The mass spec confirmation is particularly important — it proves the molecule is actually semaglutide and not a substitution.
LipidDoc_ATL said:Agreed, and mass spec answers a question purity does not: identity.
Bookmarking. The distinction being drawn above is the one nobody else makes.
Dr.PulmRoch said:I tested my certificates of analysis batch through Janoshik — 97.3% purity.
Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members. Across 51 submitted tests:
- 75% tested at ≥98% purity
- 18% tested at 95-98% purity
- 7% tested at <95% purity (concerning)
The vendors with consistently high purity results are listed in the Vendor Directory. We update monthly based on new community submissions.
PeptideDetective — Independent Peptide Analytics
Community-driven peptide testing and vendor rating platform. Transparent results. Unbiased analysis. Trusted by thousands.
View ResultsSteveThurs said:I have a certificate reporting 99.2% purity and 6.1mg content on a vial sold as 5mg, and I cannot work out whether those two numbers are consistent or…
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: good thread. Keeping it here rather than moving it, because the question is general enough to be useful. Report rather than reply if it drifts again.