Topic summary

Residual solvents and scavengers: what is looked for

Analytics › Impurities & related substances counter-ion content HPLC data table forced degradation Solved

This is a generated summary. It shows the 5 most-liked posts from a topic of 24, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

k.perrinTL2 Moderator15 Mar 2025#4

Practical note that does not fit anywhere else. Whatever you conclude from this topic, write down what you did and when. The single most useful thing in your own records is not any individual result; it is that they are dated and consecutive.

21 likes 16mo

lc_gradientTL3Analytical chemist Solution19 Mar 2025#5

a.batista, post #3: post #2 is right about the mechanism and I think understates the practical bit. Incomplete deprotection: mass higher by the protecting group mass. Usually markedly later eluting. A synthesis artifact from incomplete removal of protecting groups. Go to post

Residual solvents: traces of solvents used in purification. These are usually tested by gas chromatography, not by HPLC. A specification for residual solvents should be stated separately from the purity.

7 likes in reply to #3 16mo

s.okaforTL2 Moderator30 Mar 2025#8

On post #4 — agreed on the reasoning, with one qualification.

Disulfide formation: if a peptide contains cysteine, it can form disulfide bonds with itself or with other molecules. Under oxidising conditions multiple species appear. Reducing conditions (like DTT) convert them back.

28 likes 16mo

s.perrinTL2 Moderator9 Apr 2025#11

Aggregates: multiples of the monomer mass. May not elute at all under a standard reversed-phase method. A species that does not come off the column does not appear in the area percentage.

20 likes in reply to #3 16mo

t.waldenstrmTL2Member29 Apr 2025#18

Picking up post #15: that is the part I would want checked first.

Off-target structures: if the sequence synthesis goes wrong, a completely different amino acid can be incorporated. The resulting off-target peptide is a structural isomer with the same mass but a different sequence. No chromatographic purity method detects this without a reference standard.

29 likes 15mo

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Particulates in a reconstituted solution: identifying the likely source — what changed sinceAnalytics › Impurities & related substances · 2 replies

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