SaraMom3 said:They are not contradictory, they measure different things, and this is the single most common misreading of a certificate.
Third-party testing services for certificates of analysis besides Janoshik:
- Janoshik: Gold standard for peptide community, ~$122, 10-14 day turnaround
- Valitech: US-based, ISO 17025 accredited, ~$232
- Eurofins: Full pharmaceutical testing suite, more expensive but comprehensive
- ChemTox: Basic identity and purity testing, ~$112
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.
Following on from Dr.AddMedPHL — and this may be the naive question:
Whether a purity figure and a content figure can disagree without one of them being wrong?
BethLabQueen said:Third-party testing services for certificates of analysis besides Janoshik: Janoshik: Gold standard for peptide community, ~$122, 10-14 day turnaround…
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: 100.3% purity
Day 14: 99.1% purity
Day 28: 97.3% 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.
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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.
LibrarianMeg 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…
No disagreement with LibrarianMeg. One condition attached. One addition: an unstated method makes a report close to uninterpretable. "99% pure" without the technique, the standard and the conditions is a claim, not a measurement.