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 4 of 6

Topic	Participants	Replies	Views	Activity
Can a home kit substitute for a laboratory report? A careful no Analytics › Home & field testing third-party testing documentation quality LOD & LOQ ELISA Solved Asking directly, because I could not find a straight answer: Can a home kit substitute for a laboratory report? A careful no I would like to understand what this number means before I repeat it anywhere. A…	+122	131	1.7k	5mo
Revisiting: Sample handling between despatch and injection Analytics › Method validation recovery precision & repeatability linearity LOD & LOQ Posting this under the heading it deserves: Revisiting: Sample handling between despatch and injection Everything below is what sits behind that. Posting the method first, because I know what the first three…	+5	9	1.1k	6mo
Specificity, linearity, accuracy, precision, range, robustness — with real criteria — a second dataset Analytics › Method validation linearity LOD & LOQ recovery Closed On the subject in the title: Specificity, linearity, accuracy, precision, range, robustness — with real criteria — a second dataset Working notes rather than a conclusion. Working through the identity…	+53	58	7.5k	6mo
What a stability-indicating method is and how you demonstrate one Analytics › Method validation linearity precision & repeatability LOD & LOQ Asking directly, because I could not find a straight answer: What a stability-indicating method is and how you demonstrate one Working through the identity arithmetic and I would like it checked. retatrutide…		4	57k	6mo
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
Coming back to: "Greater than or equal to 99%" as a specification rather than a result Analytics › COA interpretation documentation quality amino acid analysis certificate of analysis batch & lot numbers Posting this under the heading it deserves: "Greater than or equal to 99%" as a specification rather than a result Everything below is what sits behind that. Working through the identity arithmetic and I…		2	31k	6mo
Second pass at: MALDI versus ESI for a quick identity check Analytics › Mass spectrometry MALDI-TOF mass error (ppm) high-resolution MS counter-ion content Solved Second pass at: MALDI versus ESI for a quick identity check 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…		2	18k	7mo
Why one laboratory's 98.4% and another's 96.1% may not contradict Analytics › Method validation stability-indicating method LOD & LOQ linearity Solved Wiki Why one laboratory's 98.4% and another's 96.1% may not contradict I have a specific reason for asking rather than idle curiosity, and the context is below. A documentation question rather than an analytical…	+28	37	457	7mo
Batch date after test date, and other internal inconsistencies Analytics › COA interpretation certificate of analysis reference standards batch & lot numbers documentation quality Batch date after test date, and other internal inconsistencies — 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…	+27	31	4.9k	7mo
An inter-laboratory comparison on one lot, tabulated — what changed since Analytics › Method validation stability-indicating method LOD & LOQ system suitability precision & repeatability An inter-laboratory comparison on one lot, tabulated — what changed since — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I…	+24	28	3.3k	7mo
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
Robustness: the parameters worth deliberately varying Analytics › Method validation stability-indicating method linearity precision & repeatability Robustness: the parameters worth deliberately varying 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…	+53	57	664	8mo
Water content on a certificate and why it changes the arithmetic — what changed since Analytics › COA interpretation documentation quality batch & lot numbers reference standards certificate of analysis On the subject in the title: Water content on a certificate and why it changes the arithmetic — what changed since Working notes rather than a conclusion. A documentation question rather than an analytical…		3	801	8mo
[2026 update] Why mass spectrometry cannot tell you about an epimer Analytics › Mass spectrometry high-resolution MS counter-ion content MALDI-TOF Why mass spectrometry cannot tell you about an epimer — 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	1k	8mo
Where the integrator drew the baseline, and how much it moved the number Analytics › HPLC & UHPLC 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
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
LOD and LOQ: definitions people get wrong Analytics › Method validation precision & repeatability recovery stability-indicating method linearity Closed LOD and LOQ: definitions people get wrong — 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 of me that…		2	43k	8mo
A comparison of home results against a laboratory result on the same vial Analytics › Home & field testing documentation quality ELISA third-party testing Posting this under the heading it deserves: A comparison of home results against a laboratory result on the same vial Everything below is what sits behind that. Working through the identity arithmetic and I…	+61	65	35k	8mo
Detection wavelength and why 214 nm and 280 nm disagree Analytics › HPLC & UHPLC 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
High-resolution MS on aggregates and what it can see Analytics › Mass spectrometry charge states counter-ion content high-resolution MS Posting this under the heading it deserves: High-resolution MS on aggregates and what it can see Everything below is what sits behind that. Working through the identity arithmetic and I would like it checked.…	+117	123	6.5k	8mo
Coming back to: Why quantitation is the hard part, not detection Analytics › Home & field testing third-party testing documentation quality ELISA LOD & LOQ Why quantitation is the hard part, not detection — 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 replies…	+86	92	54k	8mo
Particulates in a reconstituted solution: identifying the likely source Analytics › Impurities & related substances counter-ion content data table HPLC water content Posting this under the heading it deserves: Particulates in a reconstituted solution: identifying the likely source Everything below is what sits behind that. Posting the method first, because I know what the…	+15	19	13k	9mo
Lateral-flow and colorimetric approaches: the specificity problem Analytics › Home & field testing LOD & LOQ documentation quality ELISA Lateral-flow and colorimetric approaches: the specificity problem — setting out what I have, and where I think it stops being reliable. A documentation question rather than an analytical one. I have a…		2	4k	9mo
Coming back to: Resolution and tailing factor: real acceptance criteria Analytics › HPLC & UHPLC peak integration data table UV & DAD detection Posting this under the heading it deserves: Resolution and tailing factor: real acceptance criteria Everything below is what sits behind that. Posting the method first, because I know what the first three…	+93	112	5.7k	9mo
What a 2 ppm match establishes, and what it does not Analytics › Mass spectrometry high-resolution MS charge states LC-MS MALDI-TOF What a 2 ppm match establishes, and what it does not — 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…	+56	60	5.2k	9mo
A checklist for reading a certificate in under two minutes — does this still hold? Analytics › COA interpretation documentation quality certificate of analysis amino acid analysis batch & lot numbers Solved A checklist for reading a certificate in under two minutes — does this still hold? — that is the question, and I have not found it answered plainly anywhere I have looked. I would like to understand what this…	+49	55	15k	9mo
Theoretical plates: useful number or ritual? Analytics › HPLC & UHPLC 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 Analytics › HPLC & UHPLC 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
An inter-laboratory comparison on one lot, tabulated Analytics › Method validation linearity LOD & LOQ precision & repeatability system suitability Closed On the subject in the title: An inter-laboratory comparison on one lot, tabulated Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked. semaglutide has a…		3	17k	10mo