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 1 of 6

Topic	Participants	Replies	Views	Activity
About the Mass spectrometry category Analytics › Mass spectrometry LC-MS high-resolution MS mass error (ppm) Pinned Wiki LC-MS and high-resolution MS, charge states, mass accuracy in ppm, and what identity confirmation does and does not establish. This post is a community wiki: any member at trust level 3 or above can edit it,…	+5	9	19k	6h
What I would want from a home test that does not exist yet Analytics › Home & field testing ELISA documentation quality LOD & LOQ Solved Pinned The question in the title: What I would want from a home test that does not exist yet I will give what I have already checked below so nobody repeats it. A documentation question rather than an analytical…	+46	50	8k	6h
About the Impurities & related substances category Analytics › Impurities & related substances forced degradation counter-ion content water content Pinned Wiki 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…	+6	10	50k	15h
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
MS/MS sequence confirmation: what it costs and when it is worth it Analytics › Mass spectrometry LC-MS MALDI-TOF charge states Solved Pinned MS/MS sequence confirmation: what it costs and when it is worth it — 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…	+2	6	2.7k	1d
About the COA interpretation category Analytics › COA interpretation certificate of analysis documentation quality batch & lot numbers Pinned Wiki What a certificate of analysis commits its issuer to, which fields matter, and how to spot one that says almost nothing. This post is a community wiki: any member at trust level 3 or above can edit it, and…	+8	12	8.5k	2mo
About the Method validation category Analytics › Method validation stability-indicating method linearity LOD & LOQ Pinned Wiki Specificity, linearity, precision, accuracy, robustness, system suitability, and why two labs disagree. This post is a community wiki: any member at trust level 3 or above can edit it, and every edit is…	+1	5	468	5mo
Reading a home test result without over-claiming — what changed since Analytics › Home & field testing third-party testing documentation quality LOD & LOQ ELISA Pinned Closed On the subject in the title: Reading a home test result without over-claiming — what changed since Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked.…		2	12k	6mo
About the Home & field testing category Analytics › Home & field testing ELISA third-party testing LOD & LOQ Pinned Wiki What consumer-accessible tests can and cannot tell you. Mostly a subcategory about limitations. This post is a community wiki: any member at trust level 3 or above can edit it, and every edit is recorded with…		4	51k	11mo
What a simple presence test is genuinely useful for — does this still hold? Analytics › Home & field testing ELISA LOD & LOQ third-party testing documentation quality Solved Pinned What a simple presence test is genuinely useful for — does this still hold? I have a specific reason for asking rather than idle curiosity, and the context is below. I would like to understand what this…		2	22k	16mo
What consumer-accessible tests can and cannot determine Analytics › Home & field testing documentation quality ELISA third-party testing What consumer-accessible tests can and cannot determine — that is the question, and I have not found it answered plainly anywhere I have looked. Posting the method first, because I know what the first three…		2	17k	1h
Coming back to: Batch date after test date, and other internal inconsistencies Analytics › COA interpretation reference standards amino acid analysis documentation quality certificate of analysis On the subject in the title: Batch date after test date, and other internal inconsistencies Working notes rather than a conclusion. I would like to understand what this number means before I repeat it…	+21	27	420	3h
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
Reused chromatograms across lots: how to spot it Analytics › COA interpretation batch & lot numbers amino acid analysis documentation quality certificate of analysis On the subject in the title: Reused chromatograms across lots: how to spot it Working notes rather than a conclusion. A documentation question rather than an analytical one. I have a certificate in front of…	+53	60	9.5k	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
Repeatability versus intermediate precision — what changed since Analytics › Method validation recovery precision & repeatability linearity system suitability Posting this under the heading it deserves: Repeatability versus intermediate precision — what changed since Everything below is what sits behind that. Working through the identity arithmetic and I would like…		4	21k	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
Isotope patterns and why the monoisotopic peak is not the tallest — does this still hold? Analytics › Mass spectrometry charge states counter-ion content high-resolution MS mass error (ppm) Solved Isotope patterns and why the monoisotopic peak is not the tallest — does this still hold? — that is the question, and I have not found it answered plainly anywhere I have looked. Working through the identity…		2	4.6k	7h
Reading a home test result without over-claiming Analytics › Home & field testing ELISA documentation quality LOD & LOQ third-party testing Reading a home test result without over-claiming — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked. retatrutide has a…	+124	137	19k	7h
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
Coming back to: Lateral-flow and colorimetric approaches: the specificity problem Analytics › Home & field testing third-party testing LOD & LOQ documentation quality ELISA Solved On the subject in the title: Lateral-flow and colorimetric approaches: the specificity problem Working notes rather than a conclusion. I would like to understand what this number means before I repeat it…	+77	89	16k	9h
Deletion sequences: expected mass shifts by residue — the long version Analytics › Impurities & related substances water content endotoxin testing data table forced degradation On the subject in the title: Deletion sequences: expected mass shifts by residue — the long version Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked.…	+21	25	6.9k	10h
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
What consumer-accessible tests can and cannot determine — a second dataset Analytics › Home & field testing ELISA LOD & LOQ third-party testing documentation quality Solved What consumer-accessible tests can and cannot determine — a second dataset I have a specific reason for asking rather than idle curiosity, and the context is below. Posting the method first, because I know…	+117	131	45k	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
Cost versus information: making the trade-off explicitly Analytics › Home & field testing LOD & LOQ third-party testing ELISA documentation quality Cost versus information: making the trade-off explicitly Writing it up because I had to work it out twice and would rather nobody else did. Working through the identity arithmetic and I would like it checked.…	+2	6	12k	11h
A comparison of home results against a laboratory result on the same vial — does this still hold? Analytics › Home & field testing ELISA third-party testing LOD & LOQ documentation quality Solved A comparison of home results against a laboratory result on the same vial — does this still hold? I have a specific reason for asking rather than idle curiosity, and the context is below. Working through the…	+2	6	15k	11h
Reflectance and photometric devices: precision in practice — a second dataset Analytics › Home & field testing ELISA LOD & LOQ documentation quality Reflectance and photometric devices: precision in practice — a second dataset — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I…	+75	82	17k	12h
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
What a certificate commits its issuer to Analytics › COA interpretation reference standards batch & lot numbers amino acid analysis The question in the title: What a certificate commits its issuer to I will give what I have already checked below so nobody repeats it. A documentation question rather than an analytical one. I have a…	+101	116	26k	19h

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