VendorMark said:Two reports on the same product from two laboratories, four percentage points apart, and no method stated on either.
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: 99.7% purity, 0.3% total related substances. Clean chromatogram with single sharp peak at expected retention time. Exactly what you want to see.
One thing that is still open after LibrarianMeg’s answer:
Whether a purity figure and a content figure can disagree without one of them being wrong?
DataDave said:HPLC results interpretation for certificates of analysis: when you get your Janoshik report back, here's what the numbers mean: Purity %: Should be…
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: 16.6 minutes (consistent with semaglutide reference standard)
Peak purity: 98.2%
Related substances: 0.8% (single impurity at 10.4 minutes — likely a synthesis intermediate)
Mass spec: m/z 4113.5 (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.
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View ResultsOP back with an update, since a thread like this is useless without one.
Purity and content being different measurements was the piece I was missing. The vial was overfilled and pure, which is a very different problem from the one I thought I had.
Dr.RaviCardio 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:…
Agreed, and mass spec answers a question purity does not: identity. High purity tells you one thing dominates the chromatogram, not that it is the molecule you ordered. A mass within about a dalton of expected is the identity check.