Is 98% purity actually good or should I be worried — need advice

From the other side of the consultation, briefly.

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: 98.1%
Related substances: 0.7% (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.

One thing that is still open after TirzTom’s answer:

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

JenPlateau said:

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:…

Vendor quality matters when discussing certificates of analysis. I've tested my last 5 batches through Janoshik and purity has ranged from 98.6% to 99.6%. 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.

JenPlateau said:

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:…

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: two posts asking for a source have been merged into one. Please search the thread before asking again.