SleepDoc_PDX said:They are not contradictory, they measure different things, and this is the single most common misreading of a certificate.
This answered a question I did not know how to ask. I will report back once I have actually tried it.
Clinical perspective, offered as context rather than as advice.
Mass spectrometry confirmation for certificates of analysis: beyond HPLC purity, mass spec tells you the molecule's exact molecular weight. This confirms identity — not just purity.
Why this matters: HPLC can show you a "pure" compound, but if it's pure of the WRONG compound, purity is meaningless. Mass spec at m/z 4113.58 Da confirms it's actually semaglutide. My Janoshik report includes both HPLC and mass spec.
If your testing provider only offers HPLC, consider upgrading to include mass spec for at least your first batch from a new vendor.
andrew_nyc said:My vendor review relevant to certificates of analysis: ordered 5 times from my current compounder.
Vendor quality matters when discussing certificates of analysis. I've tested my last 6 batches through Janoshik and purity has ranged from 98.5% to 100.3%. 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.
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference StandardsLondonLisa said:The provenance questions are more useful than the numbers.
HPLC results interpretation for certificates of analysis: when you get your Janoshik report back, here's what the numbers mean:
My last batch: 99.3% purity, 0.1% total related substances. Clean chromatogram with single sharp peak at expected retention time. Exactly what you want to see.
Moderator note: reminder that nothing in this thread is medical advice, and that clinical claims need a source. Thread quality here is what the rules are for. Keep it up.