PurityPaulOR said:Two reports on the same product from two laboratories, four percentage points apart, and no method stated on either.
Third-party testing services for certificates of analysis besides Janoshik:
- Janoshik: Gold standard for peptide community, ~$146, 10-14 day turnaround
- Valitech: US-based, ISO 17025 accredited, ~$246
- Eurofins: Full pharmaceutical testing suite, more expensive but comprehensive
- ChemTox: Basic identity and purity testing, ~$116
Janoshik is the community standard but any ISO-accredited analytical lab can verify peptide identity and purity. The key is independence — don't rely solely on the vendor's own testing.
One thing that is still open after Dr.PulmRoch’s answer:
Whether a purity figure and a content figure can disagree without one of them being wrong?
Dr.AddMedPHL said:Third-party testing services for certificates of analysis besides Janoshik: Janoshik: Gold standard for peptide community, ~$146, 10-14 day turnaround…
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: 99.3% purity, 0.1% total related substances. Clean chromatogram with single sharp peak at expected retention time. Exactly what you want to see.
Janoshik Analytical — Independent Testing
Trusted third-party HPLC & mass spectrometry analysis. Verify peptide purity with the lab the community relies on. Independent. Accurate. Transparent.
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Est. 1998. The synthesis house behind the vials you send for testing. ISO 9001 and cGMP certified, 1,500+ staff, batch-specific COA with every order.
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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.
NurseKim_ATL said:HPLC results interpretation for certificates of analysis: when you get your Janoshik report back, here's what the numbers mean: Purity %: Should be…
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.
If somebody has the primary source to hand I would rather cite it than paraphrase it.