One thing that is still open after lisa_labSD’s answer:
How people are distinguishing a supplier having a bad batch from a supplier on the way out?
PurityPaulOR said:Prices dramatically below market are the strongest single signal, and the reason is arithmetic rather than suspicion.
Vendor quality matters when discussing certificates of analysis. I've tested my last 5 batches through Janoshik and purity has ranged from 99.0% to 99.6%. Consistency is key.
For anyone new: always request the COA, and consider independent verification. The $300 for a Janoshik test is worth the peace of mind.
PurityPaulOR said:Prices dramatically below market are the strongest single signal, and the reason is arithmetic rather than suspicion.
I tested my certificates of analysis batch through Janoshik — 98.1% purity. That's within acceptable range for compounded peptides. Turnaround was 12 business days.
The test costs ~$145 but gives you actual HPLC chromatography data plus mass spec confirmation. For the peace of mind alone, it's worth every penny. I test every new batch from a new vendor.
Trusted third-party HPLC & mass spectrometry analysis. Verify peptide purity with the lab the community relies on. Independent. Accurate. Transparent.
Verify Your PeptidesEst. 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.
Browse GL BiochemPurityPaulOR said:Prices dramatically below market are the strongest single signal, and the reason is arithmetic rather than suspicion.
Thank you for spelling out the reasoning rather than just the conclusion. Taking it to my next appointment.
From the other side of the consultation, briefly.
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: 99.0% purity
Day 14: 98.2% purity
Day 28: 99.2% 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.