Clinical perspective, offered as context rather than as advice.

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: 15.7 minutes (consistent with semaglutide reference standard)
Peak purity: 99.4%
Related substances: 0.5% (single impurity at 9.7 minutes — likely a synthesis intermediate)
Mass spec: m/z 4113.6 (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.

anders_CPH said:

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

Vendor quality matters when discussing certificates of analysis. I've tested my last 6 batches through Janoshik and purity has ranged from 97.7% to 100.7%. Consistency is key.

For anyone new: always request the COA, and consider independent verification. The $300 for a Janoshik test is worth the peace of mind.

anders_CPH said:

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

Reconstituted peptide stability data for certificates of analysis: I had Janoshik test my reconstituted vial at day 1, day 14, and day 28 stored in the refrigerator.

Day 1: 100.1% purity
Day 14: 99.6% purity
Day 28: 99.5% purity

Minimal degradation over 28 days when properly refrigerated. This confirms the standard 28-day beyond-use date is appropriate. Beyond 28 days, I'd reconstitute a fresh vial to be safe.

One thing that is still open after anders_CPH’s answer:

Did your prescriber agree with that reading, and if not what was their objection?

Moderator note: leaving this open. It is being argued well and the disagreement is the useful part. No action needed from anybody.