Has anyone dealt with moisture content analysis for lyophilized peptides?

Clinical perspective, offered as context rather than as advice.

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: 99.2% purity
Day 14: 98.2% purity
Day 28: 97.0% 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.

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.

anders_CPH said:

Mass spectrometry confirmation for certificates of analysis: beyond HPLC purity, mass spec tells you the molecule's exact molecular weight.

Adding a me-too, because a thread of one person's experience is not much use. The detail I would add is minor and it is already implied above.

anders_CPH said:

Mass spectrometry confirmation for certificates of analysis: beyond HPLC purity, mass spec tells you the molecule's exact molecular weight.

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

Shipping: Next-day with cold pack
Packaging: Professional, discreet, proper labeling with lot/batch numbers
Purity: 99.4% average across orders (Janoshik verified)
Customer service: Responsive within 2 hours
Price: $140/month for semaglutide 1.7mg equivalent

Moderator note: a post naming a supplier has been edited. Discuss suppliers in the review sections, not here. Report rather than reply if it drifts again.