c/hplc · created 14 Sep 2023
Chromatograms, methods, integration. Bring the raw trace.
Yes, probably, and this thread exists so I can link it instead of retyping it. Sources of legitimate disagreement on the same physical sample, roughly in order of how…
Method: C18 150×4.6, 5µm. 0.1% TFA in water / acetonitrile, 20→45% over 25 min. 214nm, 20µL injection. Semaglutide, reseller vial, nothing exotic. Main peak at 11.8 min…
Not naming the poster, the trace is in the thread below this one and they will know. The reported figure is 98.47%. The baseline in the attached trace drifts visibly…
Two years ago I bought a decommissioned system for less than a decent bicycle. Since then I have learned more analytical chemistry than I ever wanted and spent more…
Vendor-level purity averages over time, built from independent results rather than vendor claims. Transparent methodology, open dataset.
Browse resultsResearch peptide, not a GLP-1, from a vendor I will not name because this is a methodology question rather than a vendor post. MS confirms the expected molecular mass…
the gradient everyone uses for sema and why it under-resolves the des-amido. It comes up every few weeks and the answer has not changed. The system suitability…
peak at 4.2 min, nobody can tell me what it is, ideas. Not a hot take, just something I have not seen said plainly here. Chased a ghost peak for three weeks. It was the…
Explainer, as requested in the last thread: you cannot report area% to two decimals off that baseline. Retention time shifted 0.4 minutes and I assumed the worst. It…
two labs, same vial, 98.1 and 96.4. both right. I am not trying to be the "source?" guy. I would just like a source. Gave the same trace to two people I trust and got…
The one-line version is the title: integration decisions change your number more than the sample does. The rest is why. Carryover from a previous high-concentration…
The title is the argument: bought a second-hand HPLC. worst best decision of my life. AMA. Here is the rest of it. Carryover from a previous high-concentration…
220nm vs 214nm and what you lose at each, written plainly and without the jargon that usually swallows this topic. Gave the same trace to two people I trust and got two…
ghost peak turned out to be plumbing. always plumbing, which sounds obvious until you try to state the evidence for it. Area percent is the integrated area of your peak…
LC-MS confirmed identity but the UV purity is 94%. now what, and before anyone asks: same batch throughout, single submission, no cherry-picking between services. The…
Genuine question, and the title is the question: what is a reasonable system suitability RSD for this work. UV response is not uniform across species. At 214nm you are…
Reference standards, analytical reagents and system-suitability material. If you are running your own method, start with a known.
Reference standardsretention time shifted 0.4 min and nobody wants to talk about it. I have gone back and forth on this for months. System suitability — repeat injections, tailing factor,…
The one-line version is the title: why amino acid analysis catches the frauds HPLC misses. The rest is why. Carryover from a previous high-concentration injection looks…
does integration actually matter or is it forum lore at this point. I am not trying to be the "source?" guy. I would just like a source. System suitability — repeat…
Result first, context after: split one vial across VendorInvestigate and PeptideMeter — 98.0% and 97.9% . Everything below is how it was ordered, stored and sent. To…
method development — 14 things I got wrong before I got it right. Not a hot take, just something I have not seen said plainly here. Chased a ghost peak for three weeks.…
Right: split one vial across VendorInvestigate and PeptideMeter — 94.2% and 93.7%. I paid for this one myself, nobody sent me anything, and the receipts are in the…
The title is the argument: reading integration threads from 2024 and half of it aged badly. Here is the rest of it. GGPeps sent me the column, the gradient and the…
HPLC — what am I missing here. I would rather ask a basic question now than get this wrong quietly for two months. Chased a ghost peak for three weeks. It was the…
Question in the title, detail here: genuine question about purity that I am slightly embarrassed to ask. WWB sent me the column, the gradient and the theoretical mass…
genuine question about method development that I am slightly embarrassed to ask. Searched first, found three threads that contradict each other, hence the post.…
The analytical deep end: RP-HPLC methods, gradient design, integration decisions, LC-MS confirmation, amino-acid analysis, water content, and why two labs can report 98.1% and 96.4% on the same vial and both be right. Post the chromatogram, not the summary line.
Independent testing plus vendor-level trend data. Community-funded, unaffiliated.
peptidemeter.comSeveral compounds discussed on GLP Research Hub are sold for research use only and are not approved for human use anywhere. Nothing here is medical advice and none of it is written by your clinician. If a post reads like an instruction, treat it as a description of what one stranger did.
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