forced degradation

Named, unnamed and unspecified impurities as regulatory categories — the long version — setting out what I have, and where I think it stops being reliable. Two reports on the same lot, and I would like help…

On the subject in the title: Deletion sequences: expected mass shifts by residue — the long version Working notes rather than a conclusion. Deletion sequences keeps being re-asked here and I think that is…

On the subject in the title: Endotoxin and why it is a separate question from purity — what changed since Working notes rather than a conclusion. What changes if the standard account of Endotoxin is wrong? I…

Deletion sequences, oxidation, deamidation, aggregates, residual solvents, and counter-ion content. This post is a community wiki: any member at trust level 3 or above can edit it, and every edit is recorded…

Impurity thresholds: where the common numbers come from — setting out what I have, and where I think it stops being reliable. I have spent a fortnight trying to pin impurity thresholds down and I want to set…

Racemisation and why it is invisible to a mass measurement — what changed since Writing it up because I had to work it out twice and would rather nobody else did. What changes if the standard account of…

Second pass at: Where impurities in solid-phase peptide synthesis come from Writing it up because I had to work it out twice and would rather nobody else did. Impurities in solid-phase peptide synthesis, from…

Residual solvents and scavengers: what is looked for — what changed since — setting out what I have, and where I think it stops being reliable. What changes if the standard account of Residual solvents and…

Deletion sequences: expected mass shifts by residue — setting out what I have, and where I think it stops being reliable. Deletion sequences keeps being re-asked here and I think that is because the answer is…

Where impurities in solid-phase peptide synthesis come from Writing it up because I had to work it out twice and would rather nobody else did. Impurities in solid-phase peptide synthesis, and specifically the…

Endotoxin and why it is a separate question from purity Writing it up because I had to work it out twice and would rather nobody else did. A question about endotoxin that I think has a definite answer, unlike…

Posting this under the heading it deserves: Second pass at: Where impurities in solid-phase peptide synthesis come from Everything below is what sits behind that. Working notes on impurities in solid-phase…

The question in the title: A rising related-substance total over six months: degradation or method drift? I will give what I have already checked below so nobody repeats it. Posting the method first, because…

Trifluoroacetate content and its consequences — setting out what I have, and where I think it stops being reliable. What changes if the standard account of trifluoroacetate content is wrong? I ask because I…

Aggregates and why a purity assay may miss them entirely Writing it up because I had to work it out twice and would rather nobody else did. I would like to disagree carefully with the settled view on…

Posting this under the heading it deserves: Particulates in a reconstituted solution: identifying the likely source Everything below is what sits behind that. Something about particulates does not reconcile…

Particulates in a reconstituted solution: identifying the likely source — what changed since — setting out what I have, and where I think it stops being reliable. What changes if the standard account of…

On the subject in the title: Residual solvents and scavengers: what is looked for Working notes rather than a conclusion. I would like to know what people here actually do about residual solvents and…

Oxidation pathways for methionine and tryptophan Writing it up because I had to work it out twice and would rather nobody else did. Reading back through what has been written here about Oxidation pathways for…

Deamidation and the close-eluting pair it produces Writing it up because I had to work it out twice and would rather nobody else did. Something about deamidation does not reconcile and I would like a second…

Attributing a new peak: degradation product or excipient? I have a specific reason for asking rather than idle curiosity, and the context is below. A follow-up question about Attributing a new peak that I did…

Asking directly, because I could not find a straight answer: Attributing a new peak: degradation product or excipient? A narrow question about attributing a new peak, deliberately narrow, because the broad…

Posting this under the heading it deserves: Oxidation pathways for methionine and tryptophan Everything below is what sits behind that. Working notes on oxidation pathways for methionine rather than a…