#hplc-massspec 2025-06-20

Friday23 messages5 participantstimes are UTC

Highlights from this day

plateau_pen — the honest position is that hobby-level interpretation of a chromatogram is worth something but not much 22:12
patent_2026 — relative retention time against a standard is comparable between labs. absolute minutes are not 22:20
patent_2026 — two labs a point or two apart on the same lot is normal and gets mistaken for one of them being wrong constantly 22:45
patent_2026 — a warm transit can put a visible degradant peak on a chromatogram. that is what 22 days at ambient does 23:11
void_volume — a certificate with a number and no chromatogram is asking you to trust the integration you cannot see 23:25

plateau_pen 21:50

oxidation is about plus 15.99 Da and is usually methionine or tryptophan

patent_2026 21:55

214nm sees the amide backbone so it sees everything. 280 only sees aromatics

secretagogue_sy 21:57

thats the solvent peak

😂1📉10🔥9

secretagogue_sy 22:03

the first peak is the solvent. it is always the solvent, ask me again in a month

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

plateau_pen 22:06

plus 16 is oxidation

plateau_pen 22:12

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

patent_2026 22:13

coming back to this nobody runs enough blanks, including me

patent_2026 22:20

relative retention time against a standard is comparable between labs. absolute minutes are not

🙏4

show me the spectrum

never_for_sale 22:28

retention time is a hint

❤️17🔥17⚠️6

how much sample does a lab actually need for identity as well as purity

never_for_sale 22:37

sorry to jump in plus sixteen, is that always oxidation

[edited]

patent_2026 22:45

two labs a point or two apart on the same lot is normal and gets mistaken for one of them being wrong constantly

patent_2026 22:53

tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5

patent_2026 22:59

ms/ms or it isnt identity

void_volumelab23:02

plus 0.98 is deamidation

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

patent_2026 23:11

a warm transit can put a visible degradant peak on a chromatogram. that is what 22 days at ambient does

patent_2026 23:18

run a blank

secretagogue_sy 23:20

does retention time on its own tell you what the compound is

do the arithmetic

void_volumelab23:23

shallow gradient

a certificate with a number and no chromatogram is asking you to trust the integration you cannot see