Dr.NateNeph said:

HPLC results interpretation for certificates of analysis: when you get your Janoshik report back, here's what the numbers mean: Purity %: Should be…

Same pattern here, and in the same order. Nothing to add that would improve it.

jason_paloalto said:

Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members.

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.

jason_paloalto said:

Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members.

Bookmarking. The distinction being drawn above is the one nobody else makes.

Adding the clinical framing, because it changes how the question reads.

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: 16.8 minutes (consistent with semaglutide reference standard)
Peak purity: 99.5%
Related substances: 0.4% (single impurity at 10.7 minutes — likely a synthesis intermediate)
Mass spec: m/z 4113.5 (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.

Moderator note: the sourcing question belongs in the vendor section and has been split out. No action needed from anybody.