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 3 of 6

Topic	Participants	Replies	Views	Activity
[2026 update] Reading a chromatogram someone posted without axes Analytics › HPLC & UHPLC peak integration HPLC UV & DAD detection data table Posting this under the heading it deserves: Reading a chromatogram someone posted without axes Everything below is what sits behind that. A documentation question rather than an analytical one. I have a…		2	59	2mo
Counter-ion form: the field almost nobody reports Analytics › COA interpretation certificate of analysis documentation quality batch & lot numbers Solved Counter-ion form: the field almost nobody reports 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…		3	11k	2mo
Residual solvents and scavengers: what is looked for — what changed since Analytics › Impurities & related substances forced degradation water content data table HPLC Solved Residual solvents and scavengers: what is looked for — what changed since — setting out what I have, and where I think it stops being reliable. Posting the method first, because I know what the first three…	+37	41	7k	2mo
Reused chromatograms across lots: how to spot it — what changed since Analytics › COA interpretation batch & lot numbers amino acid analysis reference standards documentation quality Solved Reused chromatograms across lots: how to spot it — what changed since — setting out what I have, and where I think it stops being reliable. A documentation question rather than an analytical one. I have a…	+34	39	20k	2mo
Named, unnamed and unspecified impurities as regulatory categories Analytics › Impurities & related substances counter-ion content endotoxin testing water content On the subject in the title: Named, unnamed and unspecified impurities as regulatory categories Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked.…	+10	14	504	3mo
Revisiting: A field-by-field walk through a certificate of analysis Analytics › COA interpretation certificate of analysis documentation quality reference standards amino acid analysis Revisiting: 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. A documentation question rather than an analytical one. I…	+37	41	656	3mo
[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
Validating a method you did not develop Analytics › Method validation precision & repeatability recovery linearity stability-indicating method On the subject in the title: Validating a method you did not develop Working notes rather than a conclusion. I would like to understand what this number means before I repeat it anywhere. A VendorInvestigate…	+10	14	15k	3mo
Impurity thresholds: where the common numbers come from — what changed since Analytics › Impurities & related substances counter-ion content HPLC endotoxin testing water content Solved Posting this under the heading it deserves: Impurity thresholds: where the common numbers come from — what changed since Everything below is what sits behind that. A documentation question rather than an…		2	61k	3mo
Sample handling between despatch and injection Analytics › Method validation stability-indicating method LOD & LOQ linearity precision & repeatability Sample handling between despatch and injection 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 first three replies will…	+63	68	2.4k	3mo
Second pass at: Robustness: the parameters worth deliberately varying Analytics › Method validation linearity LOD & LOQ recovery system suitability On the subject in the title: Second pass at: Robustness: the parameters worth deliberately varying Working notes rather than a conclusion. I would like to understand what this number means before I repeat it…	+61	66	9.5k	3mo
Deletion sequences: expected mass shifts by residue Analytics › Impurities & related substances water content endotoxin testing forced degradation HPLC Deletion sequences: expected mass shifts by residue — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked. semaglutide has a…		2	59	3mo
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? Posting the method first, because I know what the first three…	+113	119	1.7k	3mo
Charge states for a 4 kDa peptide, worked through — the long version Analytics › Mass spectrometry LC-MS high-resolution MS mass error (ppm) Charge states for a 4 kDa peptide, worked through — the long version 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…		2	293	3mo
Where impurities in solid-phase peptide synthesis come from Analytics › Impurities & related substances water content data table HPLC endotoxin testing Solved 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 analytical one. I have a…	+54	59	14k	3mo
Shoulders, tangent skims, and defensible integration — the long version Analytics › HPLC & UHPLC 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
Endotoxin and why it is a separate question from purity Analytics › Impurities & related substances water content counter-ion content forced degradation HPLC Endotoxin and why it is a separate question from purity 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	22k	4mo
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. A documentation question rather than an analytical one. I have a…	+121	126	1.5k	4mo
Coming back to: Which fields on a certificate actually matter, ranked Analytics › COA interpretation reference standards documentation quality batch & lot numbers amino acid analysis Solved Which fields on a certificate actually matter, ranked I have a specific reason for asking rather than idle curiosity, and the context is below. Posting the method first, because I know what the first three…		2	15k	4mo
Injection volume, overload, and peak distortion — one year on Analytics › HPLC & UHPLC 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
Second pass at: Counter-ion content and its effect on measured mass Analytics › Mass spectrometry mass error (ppm) counter-ion content MALDI-TOF charge states Solved Second pass at: Counter-ion content and its effect on measured mass 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…		4	16k	4mo
Which fields on a certificate actually matter, ranked Analytics › COA interpretation reference standards certificate of analysis documentation quality batch & lot numbers Closed Which fields on a certificate actually matter, ranked — 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…	+25	29	46k	4mo
Reconciling a label claim with a content assay Analytics › COA interpretation documentation quality amino acid analysis reference standards certificate of analysis Closed On the subject in the title: Reconciling a label claim with a content assay Working notes rather than a conclusion. I would like to understand what this number means before I repeat it anywhere. A…	+2	6	183	4mo
"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. Working through the identity arithmetic and I would…	+132	146	47k	5mo
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. Working through the identity arithmetic and I would…	+107	129	41k	5mo
Second pass at: Where impurities in solid-phase peptide synthesis come from Analytics › Impurities & related substances counter-ion content data table endotoxin testing HPLC Closed Posting this under the heading it deserves: Second pass at: Where impurities in solid-phase peptide synthesis come from Everything below is what sits behind that. A documentation question rather than an…	+47	51	3.3k	5mo
Why one laboratory's 98.4% and another's 96.1% may not contradict — one year on Analytics › Method validation LOD & LOQ system suitability linearity stability-indicating method Asking directly, because I could not find a straight answer: Why one laboratory's 98.4% and another's 96.1% may not contradict — one year on Working through the identity arithmetic and I would like it…	+10	14	13k	5mo
[2026 update] A rising related-substance total over six months: degradation or method drift? Analytics › Impurities & related substances forced degradation water content endotoxin testing HPLC Solved Wiki The question in the title: A rising related-substance total over six months: degradation or method drift? I will give what I have already checked below so nobody repeats it. Posting the method first, because…	+71	78	34k	5mo
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
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. A documentation question rather than an analytical one. I have a certificate in front of me…	+123	134	31k	5mo