do you trust an area percent from a shallow gradient
#hplc-massspec 2025-09-14
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thats a charge state
a dimer usually shows up late and at roughly double the mass. the chromatogram alone will not tell you
plus 0.98 is deamidation
Verification log updated: ERP — evidence added, status unchanged.
relative retention time against a standard is comparable between labs. absolute minutes are not
my peak has a shoulder on it, what does that usually mean
if somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result
i was wrong about tailing factor. it is usually the injection or the pH, not the column
how much sample does a lab actually need for identity as well as purity
plus sixteen, is that always oxidation
within inter-lab range
semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2
is monoisotopic or average mass the one on most certificates
semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2
*PeptideMeter not the other one
tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5, i have it written down somewhere
oxidation is about plus 15.99 Da and is usually methionine or tryptophan
retention time is a hint
the honest position is that hobby-level interpretation of a chromatogram is worth something but not much
ask for the trace
if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic
Reminder set. I will post here in 9 days.
thats co-elution
ms/ms or it isnt identity
has anyone ever had a result where the mass was right and the purity was wrong
a shoulder on a peak is information, and usually bad information
Recon calculator: 30mg in 0.5ml = 4mg/ml.
😂16🙏10
whats a plus one dalton shift usually
do the arithmetic
does ms/ms actually prove identity or just make it very likely
co-elution is the failure mode that a beautiful single peak is most likely to be hiding
sorry to jump in can you tell a dimer from the chromatogram alone
Inter-lab diff for lot G-0641: 99.4% vs 99.2%. Within expected range.
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genuine question baseline is drifting badly, is that the column or the mobile phase
oxidation is about plus 15.99 Da and is usually methionine or tryptophan
baseline drift on a gradient is normal. baseline drift on an isocratic hold is your column
a dimer usually shows up late and at roughly double the mass. the chromatogram alone will not tell you
plus 16 is oxidation