HPLC vs UPLC for peptide purity — 6 month update

TinaHashiRN 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.

DoseLogDan said:

One addition: an unstated method makes a report close to uninterpretable.

This answered a question I did not know how to ask. Taking it to my next appointment.

TinaHashiRN 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: 15.8 minutes (consistent with semaglutide reference standard)
Peak purity: 98.4%
Related substances: 0.5% (single impurity at 9.2 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.

fiona_glasgow said:

I have a certificate reporting 99.2% purity and 6.1mg content on a vial sold as 5mg, and I cannot work out whether those two numbers are consistent or…

Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members. Across 63 submitted tests:

• 75% tested at ≥98% purity
• 18% tested at 95-98% purity
• 7% tested at <95% purity (concerning)

The vendors with consistently high purity results are listed in the Vendor Directory. We update monthly based on new community submissions.

Moderator note: a post naming a supplier has been edited. Discuss suppliers in the review sections, not here. No action needed from anybody.