NicoleRaleigh 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…

Agreed, with a caveat about community reputation: it is a lagging indicator. Reports arrive weeks after orders, so a supplier can look excellent for a month after quality has already changed.

NicoleRaleigh 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…

Thank you for spelling out the reasoning rather than just the conclusion. Adding it to my notes with a link back to this thread.

Adding the clinical framing, because it changes how the question reads.

Vendor quality matters when discussing certificates of analysis. I've tested my last 4 batches through Janoshik and purity has ranged from 98.3% to 100.1%. 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.

Dr.EM_Chicago said:

Vendor quality matters when discussing certificates of analysis.

This matches mine closely enough to be worth saying so out loud.

Dr.EM_Chicago said:

Vendor quality matters when discussing certificates of analysis.

Adding the part of the answer the thread has not reached. Prices dramatically below market are the strongest single signal, and the reason is arithmetic rather than suspicion. Synthesis, testing, and cold-chain shipping have floors. A price well under the floor means something was skipped, and the two things that get skipped are testing and content.