Intersection · Analytics × counter-ion content

Analytics topics tagged counter-ion content

Topics in Analytics carrying the tag counter-ion content. Acetate or TFA content and its effect on measured peptide mass.

49 topics

Topic	Participants	Replies	Views	Activity
Named, unnamed and unspecified impurities as regulatory categories — the long version 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? 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 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 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
About the Impurities & related substances category 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
Second pass at: What a 2 ppm match establishes, and what it does not 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 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 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 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 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 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 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 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 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 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 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 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 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? 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
Endotoxin and why it is a separate question from purity 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 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 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 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 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
Aggregates and why a purity assay may miss them entirely 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
Second pass at: MALDI versus ESI for a quick identity check 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
[2026 update] Why mass spectrometry cannot tell you about an epimer 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 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
High-resolution MS on aggregates and what it can see 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
Particulates in a reconstituted solution: identifying the likely source 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

Sponsored Janoshik Analytical — independent third-party testingHPLC purity and mass-spectrometric identity on submitted samples, reported with the method stated. The laboratory most often cited in this community’s verification records.Independent testing → Sponsored GL Biochem (Shanghai) Ltd. — synthesis, directFounded 1998. ISO 9001 and cGMP certified, over 1,500 staff and 200-plus patents. Custom peptide synthesis and amino acid derivatives, with a batch certificate on every order.Custom synthesis →