plus sixteen, is that always oxidation
#hplc-massspec 2026-01-15
Thursday22 messages7 participantstimes are UTC
Highlights from this day
- cross_border_cam — genuine question shallow gradients hide related substances behind the main peak. a steeper one separates and looks worse, honestly, your mileage will differ 11:08
- pharmac_pen — ok so how much sample does a lab actually need for identity as well as purity 11:10
- pharmac_pen — a dimer usually shows up late and at roughly double the mass. the chromatogram alone will not tell you relative retention time against a standard is comparable… 11:11
- VialBot — On this day 7 years ago this channel logged 54 messages. 11:20
the first peak is the solvent. it is always the solvent, still working it out
ask for the trace
plus 16 is oxidation
two labs a point or two apart on the same lot is normal and gets mistaken for one of them being wrong constantly
if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic, thats just me
can you tell a dimer from the chromatogram alone
genuine question shallow gradients hide related substances behind the main peak. a steeper one separates and looks worse, honestly, your mileage will differ
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ok so how much sample does a lab actually need for identity as well as purity
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a dimer usually shows up late and at roughly double the mass. the chromatogram alone will not tell you
relative retention time against a standard is comparable between labs. absolute minutes are not
On this day 7 years ago this channel logged 54 messages.
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quick one monoisotopic and average diverge more the bigger the molecule. say which one you are quoting
a warm transit can put a visible degradant peak on a chromatogram. that is what 15 days at ambient does
my peak has a shoulder on it, what does that usually mean
integration choices move the number by a few tenths easily. that is most of your inter-lab variance
214nm sees the amide backbone so it sees everything. 280 only sees aromatics
thats the solvent peak
deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant
integration difference
semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2
baseline is drifting badly, is that the column or the mobile phase
need more sample