Tags · Technique

counter-ion content

Acetate or TFA content and its effect on measured peptide mass.

60 topics 17 solved Synonyms: tfa Group: Technique

60 topics · page 2 of 2

Topic	Participants	Replies	Views	Activity
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. Something about MALDI versus ESI does not reconcile and I would…		2	18k	7mo
[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
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 disagree carefully with the settled…	+48	53	918	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. Something about high-resolution does not reconcile and I would like…	+117	123	6.5k	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. Something about particulates does not reconcile…	+15	19	13k	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
Deconvolution of a multiply charged envelope Analytics › Mass spectrometry MALDI-TOF charge states mass error (ppm) counter-ion content Closed Deconvolution of a multiply charged envelope — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked. tirzepatide has a…		2	63	10mo
Coming back to: Oxidation and deamidation mass shifts, tabulated Analytics › Mass spectrometry LC-MS charge states MALDI-TOF high-resolution MS Oxidation and deamidation mass shifts, tabulated — setting out what I have, and where I think it stops being reliable. Reading back through what has been written here about Oxidation and deamidation mass…	+34	38	4.8k	10mo
Second pass at: Isotonicity and what happens when you get it wrong Pharmacology › Formulation chemistry counter-ion content storage bacteriostatic water sterile water Closed Second pass at: Isotonicity and what happens when you get it wrong — setting out what I have, and where I think it stops being reliable. Something about Isotonicity does not reconcile and I would like a…	+1	5	2.6k	11mo
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
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
Particulates in a reconstituted solution: identifying the likely source — what changed since Analytics › Impurities & related substances water content HPLC forced degradation counter-ion content Particulates in a reconstituted solution: identifying the likely source — what changed since — setting out what I have, and where I think it stops being reliable. What changes if the standard account of…		2	129	14mo
Residual solvents and scavengers: what is looked for Analytics › Impurities & related substances counter-ion content HPLC data table forced degradation Solved On the subject in the title: Residual solvents and scavengers: what is looked for Working notes rather than a conclusion. I would like to know what people here actually do about residual solvents and…	+19	23	39k	14mo
Coming back to: Oxidation pathways for methionine and tryptophan Analytics › Impurities & related substances HPLC counter-ion content water content data table Oxidation pathways for methionine and tryptophan Writing it up because I had to work it out twice and would rather nobody else did. Reading back through what has been written here about Oxidation pathways for…	+1	5	36k	15mo
Deamidation and the close-eluting pair it produces Analytics › Impurities & related substances forced degradation HPLC water content data table Deamidation and the close-eluting pair it produces Writing it up because I had to work it out twice and would rather nobody else did. Something about deamidation does not reconcile and I would like a second…	+33	37	46k	15mo
Preservatives: function, testing, and limits Pharmacology › Formulation chemistry counter-ion content storage bacteriostatic water sterile water Preservatives: function, testing, and limits — setting out what I have, and where I think it stops being reliable. An honest uncertainty about preservatives rather than a disguised assertion. I do not know…	+23	27	3.7k	16mo
Oxidation and deamidation mass shifts, tabulated Analytics › Mass spectrometry counter-ion content charge states LC-MS mass error (ppm) Solved Posting this under the heading it deserves: Oxidation and deamidation mass shifts, tabulated Everything below is what sits behind that. Oxidation and deamidation mass shifts, and specifically the version of…	+67	76	21k	16mo
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
Isotope patterns and why the monoisotopic peak is not the tallest Analytics › Mass spectrometry LC-MS MALDI-TOF mass error (ppm) high-resolution MS Isotope patterns and why the monoisotopic peak is not the tallest — setting out what I have, and where I think it stops being reliable. Isotope patterns: what I expected, what I found, and the gap between…	+12	16	7.5k	17mo
Follow-up: Attributing a new peak: degradation product or excipient? Analytics › Impurities & related substances water content HPLC forced degradation endotoxin testing Solved Attributing a new peak: degradation product or excipient? I have a specific reason for asking rather than idle curiosity, and the context is below. A follow-up question about Attributing a new peak that I did…	+15	19	671	17mo
Coming back to: Adsorption to container surfaces and to plastics Pharmacology › Formulation chemistry bacteriostatic water counter-ion content storage sterile water Adsorption to container surfaces and to plastics — setting out what I have, and where I think it stops being reliable. Adsorption — I have the observation and I do not trust my interpretation of it, so I am…		2	459	17mo
Attributing a new peak: degradation product or excipient? Analytics › Impurities & related substances counter-ion content HPLC data table forced degradation Solved Closed Asking directly, because I could not find a straight answer: Attributing a new peak: degradation product or excipient? A narrow question about attributing a new peak, deliberately narrow, because the broad…		2	15k	18mo
Reading an MS report that only gives you a single number — the long version Analytics › Mass spectrometry mass error (ppm) counter-ion content LC-MS high-resolution MS Reading an MS report that only gives you a single number — the long version — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I…		2	47k	18mo
Isotonicity and what happens when you get it wrong Pharmacology › Formulation chemistry sterile water counter-ion content storage On the subject in the title: Isotonicity and what happens when you get it wrong Working notes rather than a conclusion. I was wrong about isotonicity in a thread last spring and I would like to correct it…	+27	31	11k	18mo
Oxidation pathways for methionine and tryptophan Analytics › Impurities & related substances counter-ion content data table HPLC water content Posting this under the heading it deserves: Oxidation pathways for methionine and tryptophan Everything below is what sits behind that. Working notes on oxidation pathways for methionine rather than a…	+58	63	1k	19mo
Buffers, pH and why a formulation is a formulation Pharmacology › Formulation chemistry counter-ion content cloudy or discoloured solution sterile water storage Buffers, pH and why a formulation is a formulation Writing it up because I had to work it out twice and would rather nobody else did. A formulation question rather than a pharmacological one, though the two…	+11	15	51k	21mo
Second pass at: Buffers, pH and why a formulation is a formulation Pharmacology › Formulation chemistry counter-ion content cloudy or discoloured solution sterile water Wiki Second pass at: Buffers, pH and why a formulation is a formulation Writing it up because I had to work it out twice and would rather nobody else did. Posting a small dataset on Buffers. It is mine, it is…	+24	28	1.5k	21mo
Follow-up: Trifluoroacetate content and its consequences Analytics › Impurities & related substances counter-ion content endotoxin testing HPLC data table Solved Closed On the subject in the title: Trifluoroacetate content and its consequences Working notes rather than a conclusion. A follow-up question about Trifluoroacetate content that I did not know to ask the first…	+12	16	5.7k	21mo
Coming back to: Deconvolution of a multiply charged envelope Analytics › Mass spectrometry counter-ion content charge states high-resolution MS On the subject in the title: Deconvolution of a multiply charged envelope Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked. tirzepatide has a…		2	12k	22mo
High-resolution MS on aggregates and what it can see — one year on Analytics › Mass spectrometry LC-MS counter-ion content MALDI-TOF charge states Solved High-resolution MS on aggregates and what it can see — one year on Writing it up because I had to work it out twice and would rather nobody else did. A narrow question about High-resolution, deliberately…	+54	58	1.2k	23mo