JessicaM_2024 said:

Agreed, and mass spec answers a question purity does not: identity.

Thank you — that is the clearest version of this I have read, and I have read a lot of them. Sending this to two other people who asked me the same thing last week.

Dr.GastroMayo 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…

Third-party testing services for certificates of analysis besides Janoshik:

• Janoshik: Gold standard for peptide community, ~$126, 10-14 day turnaround
• Valitech: US-based, ISO 17025 accredited, ~$236
• Eurofins: Full pharmaceutical testing suite, more expensive but comprehensive
• ChemTox: Basic identity and purity testing, ~$106

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.

anders_CPH said:

I have a certificate reporting 99.2% purity and 6.1mg content on a vial sold as 5mg, and I cannot work out whether those two numbers are consistent or…

Vendor quality matters when discussing certificates of analysis. I've tested my last 4 batches through Janoshik and purity has ranged from 98.9% to 100.5%. 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.

Moderator note: a couple of off-topic posts removed. Report rather than reply if it drifts again.