sophie_paris said:Vendor quality matters when discussing certificates of analysis.
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: 16.8 minutes (consistent with semaglutide reference standard)
Peak purity: 99.8%
Related substances: 0.4% (single impurity at 10.3 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.
Dr.PainCLE said:One addition: an unstated method makes a report close to uninterpretable.
Saving this. It is the first explanation that did not require me to already understand it.
sophie_paris said:Vendor quality matters when discussing certificates of analysis.
I tested my certificates of analysis batch through Janoshik — 97.0% purity. That's within acceptable range for compounded peptides. Turnaround was 12 business days.
The test costs ~$135 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.
Sigma-Aldrich — Research-Grade Standards
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference StandardsDr.CardioMD 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…
Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members. Across 49 submitted tests:
- 78% tested at ≥98% purity
- 15% tested at 95-98% purity
- 7% tested at <95% purity (concerning)
The vendors with consistently high purity results are listed in the Vendor Directory. We update monthly based on new community submissions.