#hplc-massspec 2026-04-24

Friday20 messages7 participantstimes are UTC

Highlights from this day

freeze_thaw — tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5, someone check my working 02:24
deamidation — how do you tell co-elution from a clean single peak 02:27
deamidation — two labs a point or two apart on the same lot is normal and gets mistaken for one of them being wrong constantly, i have it written down somewhere 06:21
split_the_cost — if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic 06:31

food_noise_off 00:18

the first peak is the solvent. it is always the solvent

food_noise_off 00:46

deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant

is uv at 214 or 280 better for peptides

food_noise_off 00:56

is a tailing factor of anything specific a problem

food_noise_off 01:28

ms/ms sequencing is the only thing i would call identity. everything else is circumstantial

food_noise_off 02:10

whats a plus one dalton shift usually

peak_splitlab02:11

i asked VendorInvestigate for the raw trace and they sent it. that is the right answer to that question

coming back after 7 months, what changed in how you read these

food_noise_off deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant

peak_splitlab02:15

run a blank

ghent_gradient 02:16

for the archive i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer

freeze_thaw 02:24

tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5, someone check my working

peak   RRT    area%    note
  1   0.42     0.31    solvent front
  2   0.88     0.44    related substance
  3   1.00    98.72    main
  4   1.14     0.53    related substance

deamidationlab02:27

how do you tell co-elution from a clean single peak

weights-monthly.csv

801 rows · not retained in the public archive

cold_start_cy 03:05

integration difference

🧊14✅1

freeze_thaw 03:37

a warm transit can put a visible degradant peak on a chromatogram. that is what 9 days at ambient does

cold_start_cy 04:17

update from 18 months ago: switched to asking for the chromatogram rather than the number and it changed everything

freeze_thaw 06:16

the honest position is that hobby-level interpretation of a chromatogram is worth something but not much

cold_start_cy 06:17

thats co-elution

deamidationlab06:21

two labs a point or two apart on the same lot is normal and gets mistaken for one of them being wrong constantly, i have it written down somewhere

two labs a point or two apart on the · 11 messages

👍11🧊17😂17

deamidation how do you tell co-elution from a clean single peak

peak_splitlab06:29

plus 0.98 is deamidation

split_the_cost 06:31

if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic

peak   RRT    area%    note
  1   0.42     0.31    solvent front
  2   0.88     0.44    related substance
  3   1.00    98.72    main
  4   1.14     0.53    related substance