Dr.SleepRoch 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. Sending this to two other people who asked me the same thing last week.
From the other side of the consultation, briefly.
Vendor quality matters when discussing certificates of analysis. I've tested my last 6 batches through Janoshik and purity has ranged from 97.9% to 100.3%. 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.
DeniseRN_TPA said:HPLC results interpretation for certificates of analysis: when you get your Janoshik report back, here's what the numbers mean: Purity %: Should be…
I tested my certificates of analysis batch through Janoshik — 99.2% purity. That's within acceptable range for compounded peptides. Turnaround was 8 business days.
The test costs ~$143 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 Standardsandrew_nyc said:The provenance questions are more useful than the numbers.
Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members. Across 59 submitted tests:
- 75% tested at ≥98% purity
- 18% 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.
Moderator note: reminder that nothing in this thread is medical advice, and that clinical claims need a source. Tagging this one for the weekly digest.