Tags · Technique

HPLC

High-performance liquid chromatography, the workhorse purity method.

48 topics 16 solved Synonyms: uhplc, rp-hplc Group: Technique

48 topics · page 1 of 2

Topic	Participants	Replies	Views	Activity
What a reversed-phase purity number actually is Analytics › HPLC & UHPLC HPLC system suitability data table peak integration Solved The question in the title: What a reversed-phase purity number actually is I will give what I have already checked below so nobody repeats it. I would like to understand what this number means before I repeat…	+87	101	27k	4h
Named, unnamed and unspecified impurities as regulatory categories — the long version Analytics › Impurities & related substances HPLC data table forced degradation counter-ion content Wiki Named, unnamed and unspecified impurities as regulatory categories — the long version — setting out what I have, and where I think it stops being reliable. A documentation question rather than an analytical…	+112	120	7.6k	5h
[2026 update] Detection wavelength and why 214 nm and 280 nm disagree Analytics › HPLC & UHPLC HPLC system suitability gradient method Detection wavelength and why 214 nm and 280 nm disagree — setting out what I have, and where I think it stops being reliable. Posting the method first, because I know what the first three replies will…	+69	76	920	6h
Follow-up: Comparing two chromatograms from different laboratories, properly Analytics › HPLC & UHPLC gradient method system suitability HPLC peak integration Comparing two chromatograms from different laboratories, properly — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I repeat it…	+62	67	12k	9h
Endotoxin and why it is a separate question from purity — what changed since Analytics › Impurities & related substances HPLC endotoxin testing data table forced degradation 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. A documentation question rather than an analytical one. I have…	+78	91	1k	10h
Why 99.2% and 97.8% on the same lot can both be correct Analytics › HPLC & UHPLC system suitability peak integration gradient method data table Solved Why 99.2% and 97.8% on the same lot can both be correct I have a specific reason for asking rather than idle curiosity, and the context is below. I would like to understand what this number means before I…	+16	20	3.1k	11h
Shoulders, tangent skims, and defensible integration Analytics › HPLC & UHPLC peak integration UV & DAD detection HPLC gradient method Posting this under the heading it deserves: Shoulders, tangent skims, and defensible integration Everything below is what sits behind that. Posting the method first, because I know what the first three…	+16	20	11k	13h
About the HPLC & UHPLC category Analytics › HPLC & UHPLC HPLC peak integration gradient method Pinned Wiki Reversed-phase separations, gradients, columns, integration, and reading a chromatogram properly. This post is a community wiki: any member at trust level 3 or above can edit it, and every edit is recorded…		4	137	18h
Gradient steepness and apparent purity: a worked comparison — the long version Analytics › HPLC & UHPLC HPLC system suitability gradient method Gradient steepness and apparent purity: a worked comparison — the long version — setting out what I have, and where I think it stops being reliable. A documentation question rather than an analytical one. I…		2	32k	1d
Impurity thresholds: where the common numbers come from Analytics › Impurities & related substances water content data table forced degradation counter-ion content Impurity thresholds: where the common numbers come from — setting out what I have, and where I think it stops being reliable. A documentation question rather than an analytical one. I have a certificate in…	+11	15	825	2d
Carryover and the ghost peak from last week's standard — what changed since Analytics › HPLC & UHPLC gradient method data table HPLC UV & DAD detection Solved Carryover and the ghost peak from last week's standard — what changed since Writing it up because I had to work it out twice and would rather nobody else did. Posting the method first, because I know what the…	+98	114	37k	22d
Second pass at: Where impurities in solid-phase peptide synthesis come from Analytics › Impurities & related substances HPLC water content counter-ion content endotoxin testing 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. A documentation question rather than an…	+4	8	7.2k	1mo
Racemisation and why it is invisible to a mass measurement Analytics › Impurities & related substances counter-ion content endotoxin testing HPLC Closed Posting this under the heading it deserves: Racemisation and why it is invisible to a mass measurement Everything below is what sits behind that. Working through the identity arithmetic and I would like it…	+120	127	41k	1mo
Resolution and tailing factor: real acceptance criteria Analytics › HPLC & UHPLC HPLC gradient method peak integration system suitability Resolution and tailing factor: real acceptance criteria Writing it up because I had to work it out twice and would rather nobody else did. I would like to understand what this number means before I repeat it…		2	15k	1mo
Injection volume, overload, and peak distortion Analytics › HPLC & UHPLC peak integration system suitability HPLC data table Solved Posting this under the heading it deserves: Injection volume, overload, and peak distortion Everything below is what sits behind that. A documentation question rather than an analytical one. I have a…	+43	47	36k	2mo
Area percent versus weight percent: the confusion that causes most arguments Analytics › HPLC & UHPLC system suitability UV & DAD detection HPLC data table Posting this under the heading it deserves: Area percent versus weight percent: the confusion that causes most arguments Everything below is what sits behind that. Posting the method first, because I know…	+10	14	2.1k	2mo
[2026 update] Reading a chromatogram someone posted without axes Analytics › HPLC & UHPLC peak integration HPLC UV & DAD detection data table Posting this under the heading it deserves: Reading a chromatogram someone posted without axes Everything below is what sits behind that. A documentation question rather than an analytical one. I have a…		2	59	2mo
Residual solvents and scavengers: what is looked for — what changed since Analytics › Impurities & related substances forced degradation water content data table HPLC Solved Residual solvents and scavengers: what is looked for — what changed since — setting out what I have, and where I think it stops being reliable. Posting the method first, because I know what the first three…	+37	41	7k	2mo
Impurity thresholds: where the common numbers come from — what changed since Analytics › Impurities & related substances counter-ion content HPLC endotoxin testing water content Solved Posting this under the heading it deserves: Impurity thresholds: where the common numbers come from — what changed since Everything below is what sits behind that. A documentation question rather than an…		2	61k	3mo
Deletion sequences: expected mass shifts by residue Analytics › Impurities & related substances water content endotoxin testing forced degradation HPLC Deletion sequences: expected mass shifts by residue — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked. semaglutide has a…		2	59	3mo
Where impurities in solid-phase peptide synthesis come from Analytics › Impurities & related substances water content data table HPLC endotoxin testing Solved 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. A documentation question rather than an analytical one. I have a…	+54	59	14k	3mo
Shoulders, tangent skims, and defensible integration — the long version Analytics › HPLC & UHPLC HPLC system suitability peak integration data table Shoulders, tangent skims, and defensible integration — the long version Writing it up because I had to work it out twice and would rather nobody else did. Posting the method first, because I know what the…	+16	20	27k	3mo
Endotoxin and why it is a separate question from purity Analytics › Impurities & related substances water content counter-ion content forced degradation HPLC 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. I would like to understand what this number means before I repeat it…		2	22k	4mo
Injection volume, overload, and peak distortion — one year on Analytics › HPLC & UHPLC system suitability peak integration gradient method data table Under review Injection volume, overload, and peak distortion — one year on Writing it up because I had to work it out twice and would rather nobody else did. A documentation question rather than an analytical one. I have…	+4	8	1.2k	4mo
Second pass at: Where impurities in solid-phase peptide synthesis come from Analytics › Impurities & related substances counter-ion content data table endotoxin testing HPLC Closed 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. A documentation question rather than an…	+47	51	3.3k	5mo
[2026 update] A rising related-substance total over six months: degradation or method drift? Analytics › Impurities & related substances forced degradation water content endotoxin testing HPLC Solved Wiki 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…	+71	78	34k	5mo
Aggregates and why a purity assay may miss them entirely Analytics › Impurities & related substances water content counter-ion content forced degradation HPLC 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. A documentation question rather than an analytical one. I have a…	+61	69	2.9k	6mo
Comparing two chromatograms from different laboratories, properly Analytics › HPLC & UHPLC peak integration system suitability UV & DAD detection gradient method Solved Closed Posting this under the heading it deserves: Comparing two chromatograms from different laboratories, properly Everything below is what sits behind that. I would like to understand what this number means…	+35	40	22k	7mo
Revisiting: Aggregates and why a purity assay may miss them entirely Analytics › Impurities & related substances endotoxin testing HPLC counter-ion content water content Solved Posting this under the heading it deserves: Revisiting: Aggregates and why a purity assay may miss them entirely Everything below is what sits behind that. I would like to understand what this number means…	+48	53	918	8mo
What a reversed-phase purity number actually is — the long version Analytics › HPLC & UHPLC gradient method system suitability HPLC UV & DAD detection Solved What a reversed-phase purity number actually is — the long version I have a specific reason for asking rather than idle curiosity, and the context is below. I would like to understand what this number means…		2	15k	8mo

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