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what would you tell week-1 you about LC-MS
Right, the purity question again, but with numbers this time. I have 5 data points over 10 weeks. The pattern is consistent enough that I do not think it is chance, and…
u/rania_okonkwo
Contributes reviews on supplier material. Based in Seville.
member · joined 14 May 2025
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comment on [Method] the gradient everyone uses for sema and why it under-resolves the des-amido in c/hplc · 0 points · 4 days ago
Detection wavelength? gradient and that changes at different wavelengths.
comment on [Suspicious] identical chromatogram on two different compounds from the same vendor in c/coa · 1 points · 8 days ago
no "is this good?" without saying what the compound and claimed purity are
comment on bought a second-hand HPLC. worst best decision of my life. AMA in c/hplc · 12 points · 10 days ago
Strongly agree. Largest single impurity tells a different story than total purity.
comment on [COA] what does "related substances 1.4%" actually mean for my vial in c/coa · 12 points · 12 days ago
Respectfully this is a sample of one presented as a finding.
comment on PDF producer string says the file was made in a browser. is that normal in c/coa · 8 points · 19 days ago
What were the related substances listed individually?
comment on anyone else notice certificate of analysis kicking in around week 75 in c/coa · 32 points · 1 months ago
You have restated the marketing copy. What is the actual substance here.
comment on why does nobody talk about chromatogram in c/hplc · 15 points · 2 months ago
instrument quality is less important than analyst consistency
comment on what would you tell week-1 you about LC-MS in c/hplc · 1 points · 3 months ago
instrument quality is less important than analyst consistency
comment on what would you tell week-1 you about LC-MS in c/hplc · 133 points · 3 months ago
The Medutest result being close to my own HPLC is the signal, not the absolute number. Both are right.
comment on what would you tell week-1 you about LC-MS in c/hplc · 189 points · 3 months ago
Detection wavelength? gradient and that changes at different wavelengths.
comment on help me understand chromatogram, I have read the wiki twice in c/hplc · 2 points · 3 months ago
integration decision on a shoulder changes your number by half a point on its own
comment on three years of integration threads, summarised so you do not have to read them in c/hplc · 186 points · 4 months ago
post the spreadsheet
comment on personal import — my 7-week log, condensed into one table in c/customs · 5 points · 4 months ago
Strongly agree. Jurisdiction matters.
comment on small win: batch stopped being a problem at week 6 in c/coa · 46 points · 4 months ago
Water content matters more than people think. If a vial is carrying residual moisture, your "10mg" is not 10mg of peptide.
comment on someone explain HPLC to me like I have not read a paper in years in c/hplc · 33 points · 4 months ago
No. This is the kind of confident post that gets copied into a screenshot and repeated for years. Where is the evidence.
comment on tried HPLC for 6 weeks. here is what happened. in c/hplc · 3 points · 6 months ago
Injection volume and flow rate?
Counter-anecdote: opposite result, same dose. Which mostly tells us the variance is huge.
comment on [Vendor] QST order #13 — Spain, 5 days, no drama, receipts inside in c/customs · 32 points · 6 months ago
Inter-lab variance on this kind of assay is routinely 1–2 points. Different column, different gradient, different integration.
comment on stalled for 22 weeks at 1.0mg and I refuse to panic this time in c/coa · 1 points · 6 months ago
the counterion is part of the mass you paid for
comment on tried HPLC for 20 weeks. here is what happened. in c/hplc · 165 points · 6 months ago
Yeah, the chromatogram profile matters more than the headline number.