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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

Topic	Participants	Replies	Views	Activity
Second pass at: A field-by-field walk through a certificate of analysis Analytics › COA interpretation certificate of analysis reference standards batch & lot numbers amino acid analysis Solved Second pass at: A field-by-field walk through a certificate of analysis Writing it up because I had to work it out twice and would rather nobody else did. The question about field-by-field walk through a…	+149	164	36k	19mo
Validating a method you did not develop — does this still hold? Analytics › Method validation stability-indicating method LOD & LOQ precision & repeatability recovery Solved Validating a method you did not develop — does this still hold? I have a specific reason for asking rather than idle curiosity, and the context is below. Validating a method, and specifically the version of…	+128	148	47k	16mo
"Greater than or equal to 99%" as a specification rather than a result Analytics › COA interpretation reference standards documentation quality batch & lot numbers amino acid analysis Solved "Greater than or equal to 99%" as a specification rather than a result Writing it up because I had to work it out twice and would rather nobody else did. Setting out an integration problem with the actual…	+132	146	47k	5mo
Coming back to: When to suspect the method rather than the sample Analytics › Method validation precision & repeatability LOD & LOQ linearity recovery Solved Wiki When to suspect the method rather than the sample I have a specific reason for asking rather than idle curiosity, and the context is below. Two reports on the same lot, and I would like help deciding whether…	+116	135	42k	19mo
Repeatability versus intermediate precision Analytics › Method validation precision & repeatability recovery LOD & LOQ linearity Solved Repeatability versus intermediate precision — setting out what I have, and where I think it stops being reliable. Trying to establish the boundary conditions on repeatability versus intermediate precision.…	+119	134	34k	13mo
When to suspect the method rather than the sample Analytics › Method validation recovery stability-indicating method linearity system suitability Solved When to suspect the method rather than the sample — that is the question, and I have not found it answered plainly anywhere I have looked. Two reports on the same lot, and I would like help deciding whether…	+109	115	63k	15mo
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 a small dataset on…	+117	131	45k	10h
Charge states for a 4 kDa peptide, worked through Analytics › Mass spectrometry high-resolution MS counter-ion content charge states LC-MS Solved On the subject in the title: Charge states for a 4 kDa peptide, worked through Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked. retatrutide has a…	+124	146	15k	16mo
Trifluoroacetate content and its consequences Analytics › Impurities & related substances water content data table forced degradation counter-ion content Trifluoroacetate content and its consequences — setting out what I have, and where I think it stops being reliable. What changes if the standard account of trifluoroacetate content is wrong? I ask because I…	+123	134	31k	5mo
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. A question about racemisation that I think has a definite…	+120	127	41k	1mo
[2026 update] Charge states for a 4 kDa peptide, worked through Analytics › Mass spectrometry counter-ion content MALDI-TOF high-resolution MS LC-MS On the subject in the title: Charge states for a 4 kDa peptide, worked through Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked. semaglutide has a…	+116	135	31k	3mo
Distinguishing a deletion sequence by mass alone Analytics › Mass spectrometry mass error (ppm) high-resolution MS LC-MS MALDI-TOF Solved Distinguishing a deletion sequence by mass alone Writing it up because I had to work it out twice and would rather nobody else did. Trying to establish the boundary conditions on distinguishing a deletion…	+121	129	25k	17mo
Counter-ion form: the field almost nobody reports — one year on Analytics › COA interpretation documentation quality reference standards batch & lot numbers On the subject in the title: Counter-ion form: the field almost nobody reports — one year on Working notes rather than a conclusion. The question about Counter-ion form that I actually want answered is the…	+121	139	31k	16mo
A field-by-field walk through a certificate of analysis Analytics › COA interpretation documentation quality amino acid analysis certificate of analysis batch & lot numbers Solved Posting this under the heading it deserves: A field-by-field walk through a certificate of analysis Everything below is what sits behind that. I have spent a fortnight trying to pin field-by-field walk…	+136	147	1.8k	12mo
Reading an MS report that only gives you a single number Analytics › Mass spectrometry counter-ion content mass error (ppm) charge states On the subject in the title: Reading an MS report that only gives you a single number Working notes rather than a conclusion. I would like to understand what this number means before I repeat it anywhere. A…	+100	113	48k	13mo
Specification in the result column: why that is a meaningful error Analytics › COA interpretation reference standards amino acid analysis certificate of analysis batch & lot numbers Under review Closed Posting this under the heading it deserves: Specification in the result column: why that is a meaningful error Everything below is what sits behind that. A documentation question rather than an analytical…	+107	129	41k	5mo
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. Collecting what is known about reading a home test result in one place, because it is…	+124	137	19k	7h
Counter-ion content and its effect on measured mass Analytics › Mass spectrometry high-resolution MS charge states MALDI-TOF LC-MS Solved On the subject in the title: Counter-ion content and its effect on measured mass Working notes rather than a conclusion. Something about counter-ion content does not reconcile and I would like a second pair…	+100	108	45k	12mo
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
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. What changes if the standard account of Carryover…	+98	114	37k	22d
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. Collecting what is known about quantitation in one place, because it…	+86	92	54k	8mo
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 disagree carefully with the settled view on home kit substitute,…	+122	131	1.7k	5mo
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. Collecting what is known about forced degradation studies…	+100	106	35k	2d
Spike-and-recover accuracy for a peptide assay Analytics › Method validation linearity system suitability stability-indicating method LOD & LOQ Wiki Posting this under the heading it deserves: Spike-and-recover accuracy for a peptide assay Everything below is what sits behind that. Asking about spike-and-recover accuracy on behalf of the question I keep…	+121	126	1.5k	4mo
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. Something about high-resolution does not reconcile and I would like…	+117	123	6.5k	8mo
What a stability-indicating method is and how you demonstrate one — one year on Analytics › Method validation precision & repeatability system suitability stability-indicating method recovery Solved What a stability-indicating method is and how you demonstrate one — one year on I have a specific reason for asking rather than idle curiosity, and the context is below. Asking about stability-indicating…	+100	112	15k	19mo
Adducts: sodium, potassium, and the peak you did not expect — does this still hold? Analytics › Mass spectrometry high-resolution MS charge states mass error (ppm) MALDI-TOF Solved Asking directly, because I could not find a straight answer: Adducts: sodium, potassium, and the peak you did not expect — does this still hold? Adducts keeps being re-asked here and I think that is because…	+113	119	1.7k	3mo
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. Two reports on the same lot, and I would like help…	+112	120	7.6k	5h
Mass error in ppm: the arithmetic and the caveat Analytics › Mass spectrometry LC-MS high-resolution MS MALDI-TOF counter-ion content Solved Mass error in ppm: the arithmetic and the caveat 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.…	+108	125	1.5k	5mo
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

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