Intersection · Analytics × gradient method

Analytics topics tagged gradient method

Topics in Analytics carrying the tag gradient method. Mobile-phase composition over time; the single biggest driver of apparent purity differences.

26 topics

Topic	Participants	Replies	Views	Activity
[2026 update] Detection wavelength and why 214 nm and 280 nm disagree 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 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
Why 99.2% and 97.8% on the same lot can both be correct 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 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 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 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
System suitability injections: if they failed, the run did not happen — the long version gradient method UV & DAD detection system suitability peak integration System suitability injections: if they failed, the run did not happen — the long version — setting out what I have, and where I think it stops being reliable. A documentation question rather than an…	+2	6	6.2k	1d
Revisiting: Theoretical plates: useful number or ritual? system suitability UV & DAD detection gradient method data table Solved Asking directly, because I could not find a straight answer: Revisiting: Theoretical plates: useful number or ritual? I would like to understand what this number means before I repeat it anywhere. A…	+16	21	1.2k	1d
[2026 update] Why 99.2% and 97.8% on the same lot can both be correct UV & DAD detection system suitability peak integration gradient method Solved Why 99.2% and 97.8% on the same lot can both be correct — that is the question, and I have not found it answered plainly anywhere I have looked. I would like to understand what this number means before I…	+1	5	719	2d
[2026 update] Area percent versus weight percent: the confusion that causes most arguments gradient method UV & DAD detection peak integration data table On the subject in the title: Area percent versus weight percent: the confusion that causes most arguments Working notes rather than a conclusion. Posting the method first, because I know what the first three…	+65	70	1.1k	16d
Carryover and the ghost peak from last week's standard — what changed since 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
Resolution and tailing factor: real acceptance criteria 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
Shoulders, tangent skims, and defensible integration — the long version 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
Injection volume, overload, and peak distortion — one year on 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
Comparing two chromatograms from different laboratories, properly 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
Where the integrator drew the baseline, and how much it moved the number system suitability gradient method UV & DAD detection data table Solved Where the integrator drew the baseline, and how much it moved the number — setting out what I have, and where I think it stops being reliable. Posting the method first, because I know what the first three…	+20	24	1.6k	8mo
What a reversed-phase purity number actually is — the long version 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
Detection wavelength and why 214 nm and 280 nm disagree peak integration UV & DAD detection system suitability HPLC On the subject in the title: Detection wavelength and why 214 nm and 280 nm disagree Working notes rather than a conclusion. Posting the method first, because I know what the first three replies will…	+78	84	1.7k	8mo
Theoretical plates: useful number or ritual? system suitability data table HPLC UV & DAD detection Solved Theoretical plates: useful number or ritual? 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 repeat it…		2	284	9mo
Coming back to: Where the integrator drew the baseline, and how much it moved the number peak integration gradient method UV & DAD detection data table On the subject in the title: Where the integrator drew the baseline, and how much it moved the number Working notes rather than a conclusion. Posting the method first, because I know what the first three…	+20	24	2.7k	10mo
Column chemistry choices for a 40-residue peptide gradient method system suitability HPLC peak integration Column chemistry choices for a 40-residue peptide — 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 otherwise be.…	+39	43	1.1k	10mo
System suitability injections: if they failed, the run did not happen peak integration HPLC data table gradient method 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. A documentation question rather than an analytical…	+23	27	6k	11mo
Reading a chromatogram someone posted without axes HPLC UV & DAD detection gradient method data table Reading a chromatogram someone posted without axes — 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 front…	+47	55	9.4k	13mo
Area percent versus weight percent: the confusion that causes most arguments — what changed since gradient method data table HPLC 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. Posting the method first,…	+30	34	40k	13mo
Coming back to: Column chemistry choices for a 40-residue peptide peak integration system suitability gradient method data table On the subject in the title: Column chemistry choices for a 40-residue peptide Working notes rather than a conclusion. Posting the method first, because I know what the first three replies will otherwise be.…		2	43k	16mo
Why I ask for the gradient before I discuss the number gradient method data table HPLC system suitability 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…	+35	39	4.9k	20mo

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