How to read a Certificate of Analysis — complete guide

PharmacoVig_BOS said:

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

My vendor review relevant to certificates of analysis: ordered 4 times from my current compounder. Consistency has been excellent.

Shipping: 2-day priority with gel ice
Packaging: Professional, discreet, proper labeling with lot/batch numbers
Purity: 98.5% average across orders (Janoshik verified)
Customer service: Responsive within 4 hours
Price: $125/month for tirzepatide 10mg equivalent

PharmacoVig_BOS said:

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

I tested my certificates of analysis batch through Janoshik — 99.8% purity. That's within acceptable range for compounded peptides. Turnaround was 10 business days.

The test costs ~$128 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.

PharmacoVig_BOS said:

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

Saving this. It is the first explanation that did not require me to already understand it.

From the other side of the consultation, briefly.

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: 15.2 minutes (consistent with semaglutide reference standard)
Peak purity: 98.1%
Related substances: 0.8% (single impurity at 9.0 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.

LindaRN_retired 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:…

This matches mine closely enough to be worth saying so out loud. The detail I would add is minor and it is already implied above.