Jun 8, 2026 at 11:18 AM#1
Got my latest Janoshik results back and I realized a lot of people in this community don't actually know how to read an HPLC report. I work in analytical chemistry (pharma sector) so let me break this down.
What you'll see on a Janoshik HPLC report:
1. Chromatogram — the actual graph with peaks. X-axis is retention time (minutes), Y-axis is signal intensity (mAU)
2. Peak table — lists each detected peak, its retention time, area, and area %
3. Purity percentage — the main peak area as a % of total peak area
4. Identity confirmation — whether the main peak's retention time matches the reference standard
What "good" results look like for GLP-1 peptides:
- Purity ≥ 95% = excellent, pharmaceutical grade territory
- Purity 90-95% = acceptable for research peptides
- Purity 85-90% = borderline, I'd want to know what the impurities are
- Purity < 85% = return/discard, not worth the risk
The purity number is the single most important figure. But don't ignore the rest of the data. 📊
39 9steve_okc, dave_SLC, FDA_TrackerJim and 36 others
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Jun 8, 2026 at 11:21 AM#2
This is so helpful. I just got my first result back — tirzepatide from [vendor]. Report says 97.3% purity with a main peak at retention time 12.4 min. There are two small impurity peaks at 8.2 min (1.1%) and 14.7 min (1.6%).
Is this good? Should I be worried about those impurity peaks?
Last edited: Jun 8, 2026 at 1:21 PM
38 8HealthEcon_DC, PedsEndoPhilly, SleepDoc_PDX and 35 others
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Jun 8, 2026 at 11:23 AM#3
97.3% is excellent — that's genuinely pharmaceutical grade purity. For context, the FDA approval for Mounjaro (brand tirzepatide) requires ≥95% purity.
Those small impurity peaks at 1.1% and 1.6% are completely normal and expected in peptide synthesis. They're most likely:
- Truncated sequences — shorter versions of the peptide that didn't fully synthesize
- Oxidized forms — the peptide with a slightly modified amino acid
- Deletion peptides — missing one amino acid in the chain
None of these are dangerous at those levels. They're just inactive or minimally active fragments. You'd need impurities above 5% before I'd start asking questions about what they actually are.
Your vendor did well on this batch. 👍
37 7julia.endo, JessicaM_2024, TomFromTexas and 34 others
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Sigma-Aldrich — Research-Grade Standards
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference StandardsJun 8, 2026 at 11:26 AM#4
Good breakdown. Let me add something about retention time because this is how identity is confirmed.
Every compound has a characteristic retention time on a given HPLC column under specific conditions. Janoshik runs reference standards alongside your sample. If your sample's main peak elutes at the same time (±0.2 min typically) as the reference standard, that confirms identity.
> If the purity is 98% but the retention time doesn't match the reference standard, you have a very pure sample of the wrong compound.
This has happened. I've seen a result where someone sent in "semaglutide" and it came back 96% pure — but the retention time matched BPC-157, not semaglutide. The vendor had mislabeled the vials. Without the identity confirmation, you'd think everything was fine.
Always check the identity match, not just the purity number.
36 6RegAffairsDC, BiostatsBrad, PeptideSynthNJ and 33 others
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