NurseKim_ATL 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.
Dr.Martinez said:Agreed, and mass spec answers a question purity does not: identity.
This is exactly what I could not find anywhere else. Sending this to two other people who asked me the same thing last week.
NurseKim_ATL 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…
HPLC results interpretation for certificates of analysis: when you get your Janoshik report back, here's what the numbers mean:
- Purity %: Should be >97%. Below 95% is concerning.
- Retention time: Should match reference standard for the peptide
- Related substances: Degradation products should be <2% total
- Single impurity: No individual impurity should exceed 1%
My last batch: 99.4% purity, 0.2% total related substances. Clean chromatogram with single sharp peak at expected retention time. Exactly what you want to see.
Sigma-Aldrich — Research-Grade Standards
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference StandardsSkepticalSean said:Two reports on the same product from two laboratories, four percentage points apart, and no method stated on either.
My vendor review relevant to certificates of analysis: ordered 5 times from my current compounder. Consistency has been excellent.
Shipping: Same-day local pickup
Packaging: Professional, discreet, proper labeling with lot/batch numbers
Purity: 98.2% average across orders (Janoshik verified)
Customer service: Responsive within 6 hours
Price: $122/month for tirzepatide 10mg equivalent
Moderator note: good thread. Keeping it here rather than moving it, because the question is general enough to be useful. Tagging this one for the weekly digest.