james_edin said:They are not contradictory, they measure different things, and this is the single most common misreading of a certificate.
Genuinely useful, thank you. I had the facts and not the framework. I will report back once I have actually tried it.
Adding the clinical framing, because it changes how the question reads.
Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members. Across 56 submitted tests:
- 85% tested at ≥98% purity
- 10% tested at 95-98% purity
- 5% 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.
GenomicsKate said:Mass spectrometry confirmation for certificates of analysis: beyond HPLC purity, mass spec tells you the molecule's exact molecular weight.
COA red flags for certificates of analysis — here's what to look for when reviewing a Certificate of Analysis:
- No HPLC data: If there's no chromatography graph, it's not a real COA
- Exact 100% purity: Suspicious — real testing always shows slight variation
- No batch number: Can't trace back to specific production
- No endotoxin testing: For injectables, this is essential
- Template looks like it was made in Word: Professional labs have standardized formats
I have seen fake COAs that are literally photoshopped. Always verify independently if possible.
Sigma-Aldrich — Research-Grade Standards
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.
I tested my certificates of analysis batch through Janoshik — 97.6% purity. That's within acceptable range for compounded peptides. Turnaround was 14 business days.
The test costs ~$144 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.
Moderator note: a post naming a supplier has been edited. Discuss suppliers in the review sections, not here. Tagging this one for the weekly digest.