LC-MS/MS vs HPLC for peptide analysis — November 2025

claudia_zurich 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…

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.

SallyK_inj said:

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

Thank you for spelling out the reasoning rather than just the conclusion. I will report back once I have actually tried it.

claudia_zurich 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…

My HPLC chromatogram analysis for certificates of analysis — I sent my batch to Janoshik and here's what the results showed:

Main peak retention time: 15.3 minutes (consistent with semaglutide reference standard)
Peak purity: 98.7%
Related substances: 0.4% (single impurity at 9.0 minutes — likely a synthesis intermediate)
Mass spec: m/z 4113.6 (matches expected molecular weight)

This is a clean result. The mass spec confirmation is particularly important — it proves the molecule is actually semaglutide and not a substitution.

HealthEcon_DC said:

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

I tested my certificates of analysis batch through Janoshik — 98.1% 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.

Moderator note: the sourcing question belongs in the vendor section and has been split out.