Understanding peptide purity percentages — what worked for you?

NurseLeah_Nash said:

Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members.

This is my experience too, for whatever a second data point is worth.

jason_paloalto said:

Vendor quality matters when discussing certificates of analysis.

I tested my certificates of analysis batch through Janoshik — 99.5% 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.

jason_paloalto said:

Vendor quality matters when discussing certificates of analysis.

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.

One thing that is still open after jason_paloalto’s answer:

How would you tell the difference between that and the alternative explanation?

Moderator note: two posts asking for a source have been merged into one. Please search the thread before asking again. Thread quality here is what the rules are for. Keep it up.