PharmacoVig_BOS said:The provenance questions are more useful than the numbers.
This answered a question I did not know how to ask. Adding it to my notes with a link back to this thread.
From the other side of the consultation, briefly.
Vendor quality matters when discussing certificates of analysis. I've tested my last 3 batches through Janoshik and purity has ranged from 99.2% to 99.0%. 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: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 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.
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference StandardsDr.KarenChen said:Inter-laboratory variation comes from real methodological differences, not sloppiness: which reference standard was used and how it was itself…
My HPLC chromatogram analysis for certificates of analysis — I sent my batch to Janoshik and here's what the results showed:
Main peak retention time: 16.6 minutes (consistent with semaglutide reference standard)
Peak purity: 98.2%
Related substances: 0.8% (single impurity at 10.4 minutes — likely a synthesis intermediate)
Mass spec: m/z 4113.5 (matches expected molecular weight)
This is a clean result. The mass spec confirmation is particularly important — it proves the molecule is actually semaglutide and not a substitution.