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 1 of 2

Topic	Participants	Replies	Views	Activity
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
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
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
Coming back to: Solubility limits and what a cloudy solution is telling you Pharmacology › Formulation chemistry sterile water cloudy or discoloured solution storage counter-ion content On the subject in the title: Solubility limits and what a cloudy solution is telling you Working notes rather than a conclusion. A documentation question rather than an analytical one. I have a certificate in…	+38	43	29k	13h
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
Solubility limits and what a cloudy solution is telling you Pharmacology › Formulation chemistry cloudy or discoloured solution storage counter-ion content Solubility limits and what a cloudy solution is telling you — 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…	+11	15	34k	20h
Second pass at: What a 2 ppm match establishes, and what it does not Analytics › Mass spectrometry MALDI-TOF mass error (ppm) counter-ion content high-resolution MS Second pass at: What a 2 ppm match establishes, and what it does not — setting out what I have, and where I think it stops being reliable. Working through the identity arithmetic and I would like it checked.…	+44	49	8.1k	1d
Mass error in ppm: the arithmetic and the caveat — a second dataset Analytics › Mass spectrometry counter-ion content mass error (ppm) charge states LC-MS Solved On the subject in the title: Mass error in ppm: the arithmetic and the caveat — a second dataset Working notes rather than a conclusion. Working through the identity arithmetic and I would like it checked.…	+20	24	1.7k	1d
Impurity thresholds: where the common numbers come from Analytics › Impurities & related substances water content data table forced degradation counter-ion content Impurity thresholds: where the common numbers come from — 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…	+11	15	825	2d
Racemisation and why it is invisible to a mass measurement — what changed since Analytics › Impurities & related substances forced degradation water content counter-ion content Racemisation and why it is invisible to a mass measurement — what changed since Writing it up because I had to work it out twice and would rather nobody else did. Working through the identity arithmetic and I…	+11	15	42k	16d
Deamidation and the close-eluting pair it produces — the long version Analytics › Impurities & related substances counter-ion content endotoxin testing data table Posting this under the heading it deserves: Deamidation and the close-eluting pair it produces — the long version Everything below is what sits behind that. I would like to understand what this number means…		3	347	24d
MS/MS sequence confirmation: what it costs and when it is worth it — what changed since Analytics › Mass spectrometry charge states LC-MS MALDI-TOF counter-ion content Closed Posting this under the heading it deserves: MS/MS sequence confirmation: what it costs and when it is worth it — what changed since Everything below is what sits behind that. Working through the identity…	+34	39	21k	1mo
Second pass at: Where impurities in solid-phase peptide synthesis come from Analytics › Impurities & related substances HPLC water content counter-ion content endotoxin testing Second pass at: 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…	+4	8	7.2k	1mo
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. Working through the identity arithmetic and I would like it…	+120	127	41k	1mo
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
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
[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
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
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
[2026 update] Buffers, pH and why a formulation is a formulation Pharmacology › Formulation chemistry counter-ion content storage bacteriostatic water cloudy or discoloured solution Posting this under the heading it deserves: Buffers, pH and why a formulation is a formulation Everything below is what sits behind that. Working through the identity arithmetic and I would like it checked.…		2	773	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
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
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
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
Adsorption to container surfaces and to plastics Pharmacology › Formulation chemistry cloudy or discoloured solution counter-ion content sterile water bacteriostatic water On the subject in the title: Adsorption to container surfaces and to plastics Working notes rather than a conclusion. A documentation question rather than an analytical one. I have a certificate in front of…	+13	17	4.3k	5mo
Lyophilisation and why the cake looks the way it does Pharmacology › Formulation chemistry sterile water bacteriostatic water storage cloudy or discoloured solution Posting this under the heading it deserves: Lyophilisation and why the cake looks the way it does Everything below is what sits behind that. I would like to understand what this number means before I repeat…	+33	37	60k	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

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