bbq_ray_KC said:

Agreed, and mass spec answers a question purity does not: identity.

That reframing is the part I needed. Sending this to two other people who asked me the same thing last week.

Dr.GastroMayo said:

Reconstituted peptide stability data for certificates of analysis: I had Janoshik test my reconstituted vial at day 1, day 14, and day 28 stored in…

I tested my certificates of analysis batch through Janoshik — 98.7% purity. That's within acceptable range for compounded peptides. Turnaround was 12 business days.

The test costs ~$127 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.

tyler_CSCS said:

Two reports on the same product from two laboratories, four percentage points apart, and no method stated on either.

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.

Moderator note: the sourcing question belongs in the vendor section and has been split out. Report rather than reply if it drifts again.