Dr.AddMedPHL 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.
Correct me if the detail matters more than I have assumed.
Dr.GastroMayo said:Two reports on the same product from two laboratories, four percentage points apart, and no method stated on either.
Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members. Across 57 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.
DataDave said:I am more sceptical of certificates as a category than this thread is.
I tested my certificates of analysis batch through Janoshik — 98.4% purity. That's within acceptable range for compounded peptides. Turnaround was 10 business days.
The test costs ~$136 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.
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 RegAffairsDC — and this may be the naive question:
Why two laboratories report different purity for the same batch, and which number to believe?
OP back with an update, since a thread like this is useless without one.
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.