20 categories

Analytics

Analytical chemistry: chromatography, mass spectrometry, certificates of analysis, impurity profiles and method validation. The most technical part of the site.

178 topics8,388 posts59 solved Moderators: j.mwangi, KLindqvist About this category

HPLC & UHPLC 35 Mass spectrometry 30 COA interpretation 33 Impurities & related substances 30 Method validation 28 Home & field testing 22

178 topics · page 2 of 6

Topic	Participants	Replies	Views	Activity
Revisiting: Spike-and-recover accuracy for a peptide assay Analytics › Method validation LOD & LOQ system suitability stability-indicating method linearity Revisiting: Spike-and-recover accuracy for a peptide assay — 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 anywhere.…		2	6.8k	21h
What I would want from a home test that does not exist yet — what changed since Analytics › Home & field testing third-party testing LOD & LOQ documentation quality ELISA Solved Asking directly, because I could not find a straight answer: What I would want from a home test that does not exist yet — what changed since Posting the method first, because I know what the first three…	+101	111	1.9k	21h
Second pass at: Cost versus information: making the trade-off explicitly Analytics › Home & field testing third-party testing documentation quality ELISA Posting this under the heading it deserves: Second pass at: Cost versus information: making the trade-off explicitly Everything below is what sits behind that. Working through the identity arithmetic and I…	+23	27	6.1k	22h
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
System suitability injections: if they failed, the run did not happen — the long version Analytics › HPLC & UHPLC 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
Second pass at: What a 2 ppm match establishes, and what it does not Analytics › Mass spectrometry MALDI-TOF mass error (ppm) counter-ion content high-resolution MS Second pass at: What a 2 ppm match establishes, and what it does not — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked.…	+44	49	8.1k	1d
What a certificate commits its issuer to — one year on Analytics › COA interpretation reference standards certificate of analysis documentation quality batch & lot numbers Wiki What a certificate commits its issuer to — one year on — that is the question, and I have not found it answered plainly anywhere I have looked. A documentation question rather than an analytical one. I have a…	+107	117	6.5k	1d
What a simple presence test is genuinely useful for Analytics › Home & field testing documentation quality ELISA third-party testing LOD & LOQ Solved What a simple presence test is genuinely useful for — that is the question, and I have not found it answered plainly anywhere I have looked. Working through the identity arithmetic and I would like it…		2	58	1d
Revisiting: Can a home kit substitute for a laboratory report? A careful no Analytics › Home & field testing ELISA LOD & LOQ documentation quality third-party testing Revisiting: Can a home kit substitute for a laboratory report? A careful no — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it…	+50	56	9.8k	1d
Revisiting: Theoretical plates: useful number or ritual? Analytics › HPLC & UHPLC 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
Specificity, linearity, accuracy, precision, range, robustness — with real criteria Analytics › Method validation precision & repeatability LOD & LOQ linearity Specificity, linearity, accuracy, precision, range, robustness — with real 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…	+44	48	12k	1d
Mass error in ppm: the arithmetic and the caveat — a second dataset Analytics › Mass spectrometry counter-ion content mass error (ppm) charge states LC-MS Solved On the subject in the title: Mass error in ppm: the arithmetic and the caveat — a second dataset Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked.…	+20	24	1.7k	1d
What a certificate commits its issuer to — the long version Analytics › COA interpretation batch & lot numbers amino acid analysis reference standards certificate of analysis Asking directly, because I could not find a straight answer: What a certificate commits its issuer to — the long version A documentation question rather than an analytical one. I have a certificate in front…	+20	26	21k	2d
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
Forced degradation studies: designing one that is informative Analytics › Method validation precision & repeatability recovery stability-indicating method Under review Posting this under the heading it deserves: Forced degradation studies: designing one that is informative Everything below is what sits behind that. Working through the identity arithmetic and I would like it…	+100	106	35k	2d
[2026 update] Why 99.2% and 97.8% on the same lot can both be correct Analytics › HPLC & UHPLC 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
Coming back to: Specificity, linearity, accuracy, precision, range, robustness — with real criteria Analytics › Method validation linearity recovery precision & repeatability system suitability On the subject in the title: Specificity, linearity, accuracy, precision, range, robustness — with real criteria Working notes rather than a conclusion. Posting the method first, because I know what the first…	+93	99	1.4k	6d
Follow-up: Reconciling a label claim with a content assay Analytics › COA interpretation reference standards documentation quality batch & lot numbers amino acid analysis Reconciling a label claim with a content assay 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 anywhere.…	+26	30	6.5k	14d
Racemisation and why it is invisible to a mass measurement — what changed since Analytics › Impurities & related substances forced degradation water content counter-ion content 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. Working through the identity arithmetic and I…	+11	15	42k	16d
[2026 update] Area percent versus weight percent: the confusion that causes most arguments Analytics › HPLC & UHPLC 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 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
Deamidation and the close-eluting pair it produces — the long version Analytics › Impurities & related substances counter-ion content endotoxin testing data table Posting this under the heading it deserves: Deamidation and the close-eluting pair it produces — the long version Everything below is what sits behind that. I would like to understand what this number means…		3	347	24d
Purity assay versus content assay: two different numbers Analytics › COA interpretation documentation quality batch & lot numbers reference standards certificate of analysis On the subject in the title: Purity assay versus content assay: two different numbers Working notes rather than a conclusion. I would like to understand what this number means before I repeat it anywhere. A…	+6	10	24k	25d
A checklist for reading a certificate in under two minutes Analytics › COA interpretation certificate of analysis batch & lot numbers amino acid analysis Solved A checklist for reading a certificate in under two minutes — 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 anywhere.…	+39	46	38k	1mo
MS/MS sequence confirmation: what it costs and when it is worth it — what changed since Analytics › Mass spectrometry charge states LC-MS MALDI-TOF counter-ion content Closed Posting this under the heading it deserves: MS/MS sequence confirmation: what it costs and when it is worth it — what changed since Everything below is what sits behind that. Working through the identity…	+34	39	21k	1mo
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