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

Clinical perspective, offered as context rather than as advice.

My vendor review relevant to certificates of analysis: ordered 5 times from my current compounder. Consistency has been excellent.

Shipping: Same-day local pickup
Packaging: Professional, discreet, proper labeling with lot/batch numbers
Purity: 97.6% average across orders (Janoshik verified)
Customer service: Responsive within 6 hours
Price: $150/month for semaglutide 2.4mg equivalent

DoseLogDan said:

HPLC results interpretation for certificates of analysis: when you get your Janoshik report back, here's what the numbers mean: Purity %: Should be…

Vendor quality matters when discussing certificates of analysis. I've tested my last 3 batches through Janoshik and purity has ranged from 98.8% to 99.4%. 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.

Following on from DoseLogDan — and this may be the naive question:

Did your prescriber agree with that reading, and if not what was their objection?

TrialTracker_MD said:

Vendor quality matters when discussing certificates of analysis.

I tested my certificates of analysis batch through Janoshik — 99.2% purity. That's within acceptable range for compounded peptides. Turnaround was 14 business days.

The test costs ~$146 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. Thread quality here is what the rules are for. Keep it up.