Batch-to-batch purity variation — looking for input

pete_nash said:

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…

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.

NurseKim_ATL said:

One addition: an unstated method makes a report close to uninterpretable.

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.

pete_nash said:

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…

Vendor quality matters when discussing certificates of analysis. I've tested my last 5 batches through Janoshik and purity has ranged from 97.8% to 99.2%. 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.EndoIndy 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…

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: 97.5% average across orders (Janoshik verified)
Customer service: Responsive within 4 hours
Price: $133/month for semaglutide 2.4mg equivalent

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