Dr.SleepRoch said:

COA red flags for certificates of analysis — here's what to look for when reviewing a Certificate of Analysis: No HPLC data: If there's no…

Vendor quality matters when discussing certificates of analysis. I've tested my last 6 batches through Janoshik and purity has ranged from 98.7% to 100.3%. 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.

Dr.NephBHM_UK said:

Agreed, and mass spec answers a question purity does not: identity.

Thank you — that is the clearest version of this I have read, and I have read a lot of them. Taking it to my next appointment.

Dr.SleepRoch said:

COA red flags for certificates of analysis — here's what to look for when reviewing a Certificate of Analysis: No HPLC data: If there's no…

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: 99.3%
Related substances: 0.5% (single impurity at 8.5 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.

jennifer_SEA 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…

I tested my certificates of analysis batch through Janoshik — 98.7% purity. That's within acceptable range for compounded peptides. Turnaround was 8 business days.

The test costs ~$145 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.

Moderator note: leaving this open. It is being argued well and the disagreement is the useful part. Tagging this one for the weekly digest.