HPLC vs UPLC for peptide purity — method comparison study

Dr.GutHealth 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:…

Same pattern here, and in the same order. I had assumed I was the exception until I read this.

Dr.RaviCardio said:

My vendor review relevant to certificates of analysis: ordered 3 times from my current compounder.

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.

Dr.RaviCardio said:

My vendor review relevant to certificates of analysis: ordered 3 times from my current compounder.

This is exactly what I could not find anywhere else. Adding it to my notes with a link back to this thread.

Clinical perspective, offered as context rather than as advice.

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: reminder that nothing in this thread is medical advice, and that clinical claims need a source.