Dr.PulmRoch said:They are not contradictory, they measure different things, and this is the single most common misreading of a certificate.
Saving this. It is the first explanation that did not require me to already understand it. Printing the relevant bit and taking it with me.
Clinical perspective, offered as context rather than as advice.
Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members. Across 48 submitted tests:
The vendors with consistently high purity results are listed in the Vendor Directory. We update monthly based on new community submissions.
PharmHunterJen said:HPLC results interpretation for certificates of analysis: when you get your Janoshik report back, here's what the numbers mean: Purity %: Should be…
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 Standardskate.chem said:The provenance questions are more useful than the numbers.
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: 15.4 minutes (consistent with semaglutide reference standard)
Peak purity: 98.7%
Related substances: 0.6% (single impurity at 9.2 minutes — likely a synthesis intermediate)
Mass spec: m/z 4113.6 (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.
Moderator note: two posts asking for a source have been merged into one. Please search the thread before asking again. Thread quality here is what the rules are for. Keep it up.