Dr.RaviCardio said:The provenance questions are more useful than the numbers.
I am more sceptical of certificates as a category than this thread is. The document tells you about a sample somebody chose to send, at a moment in time, and nothing about the vial in your hand. Independent purchase-and-test is a different quality of evidence and everything else is inference.
mark_tokyo said:Two reports on the same product from two laboratories, four percentage points apart, and no method stated on either.
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: 16.3 minutes (consistent with semaglutide reference standard)
Peak purity: 98.2%
Related substances: 0.7% (single impurity at 10.2 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.
LarryQC_SD said:I am more sceptical of certificates as a category than this thread is.
My vendor review relevant to certificates of analysis: ordered 4 times from my current compounder. Consistency has been excellent.
Shipping: 2-day priority with gel ice
Packaging: Professional, discreet, proper labeling with lot/batch numbers
Purity: 99.1% average across orders (Janoshik verified)
Customer service: Responsive within 4 hours
Price: $137/month for semaglutide 1.7mg equivalent
Janoshik Analytical — Independent Testing
Trusted third-party HPLC & mass spectrometry analysis. Verify peptide purity with the lab the community relies on. Independent. Accurate. Transparent.
Verify Your PeptidesGL Biochem (Shanghai) Ltd. — Direct Manufacturer
Est. 1998. The synthesis house behind the vials you send for testing. ISO 9001 and cGMP certified, 1,500+ staff, batch-specific COA with every order.
Browse GL BiochemFollowing on from pam_columbus — and this may be the naive question:
Why two laboratories report different purity for the same batch, and which number to believe?
Reporting back.
Purity and content being different measurements was the piece I was missing. The vial was overfilled and pure, which is a very different problem from the one I thought I had.