HPLC

On the subject in the title: Detection wavelength and why 214 nm and 280 nm disagree Working notes rather than a conclusion. I would like to disagree carefully with the settled view on detection wavelength,…

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…

Theoretical plates: useful number or ritual? I have a specific reason for asking rather than idle curiosity, and the context is below. Asking about theoretical plates directly, because I have read four…

Column chemistry choices for a 40-residue peptide — setting out what I have, and where I think it stops being reliable. Collecting what is known about column chemistry choices in one place, because it is…

Posting this under the heading it deserves: System suitability injections: if they failed, the run did not happen Everything below is what sits behind that. Proposing that system suitability injections…

Reading a chromatogram someone posted without axes — setting out what I have, and where I think it stops being reliable. Posting a small dataset on reading a chromatogram. It is mine, it is uncontrolled, and…

Area percent versus weight percent: the confusion that causes most arguments — what changed since Writing it up because I had to work it out twice and would rather nobody else did. What changes if the…

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…

The question in the title: Why I ask for the gradient before I discuss the number I will give what I have already checked below so nobody repeats it. I would like to understand what this number means before I…

On the subject in the title: Trifluoroacetate content and its consequences Working notes rather than a conclusion. A follow-up question about Trifluoroacetate content that I did not know to ask the first…

On the subject in the title: Gradient steepness and apparent purity: a worked comparison Working notes rather than a conclusion. I have spent a fortnight trying to pin gradient steepness and apparent purity…

Asking directly, because I could not find a straight answer: A rising related-substance total over six months: degradation or method drift? Rising related-substance — I have the observation and I do not trust…