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

Adding the clinical framing, because it changes how the question reads.

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 the refrigerator.

Day 1: 100.1% purity
Day 14: 99.6% purity
Day 28: 97.3% purity

Minimal degradation over 28 days when properly refrigerated. This confirms the standard 28-day beyond-use date is appropriate. Beyond 28 days, I'd reconstitute a fresh vial to be safe.

raj_cambridge said:

Vendor quality matters when discussing certificates of analysis.

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: 97.2% average across orders (Janoshik verified)
Customer service: Responsive within 6 hours
Price: $138/month for semaglutide 2.4mg equivalent

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

What would you measure differently if you were starting again?

Dr.NateNeph said:

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

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: a post naming a supplier has been edited. Discuss suppliers in the review sections, not here. Report rather than reply if it drifts again.