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 6 of 6

Topic	Participants	Replies	Views	Activity
Carryover and the ghost peak from last week's standard Analytics › HPLC & UHPLC data table UV & DAD detection peak integration system suitability On the subject in the title: Carryover and the ghost peak from last week's standard Working notes rather than a conclusion. Posting the method first, because I know what the first three replies will otherwise…	+80	92	16k	16mo
A certificate with no method stated: what can you conclude? Analytics › COA interpretation certificate of analysis batch & lot numbers documentation quality Solved A certificate with no method stated: what can you conclude? I have a specific reason for asking rather than idle curiosity, and the context is below. I would like to understand what this number means before I…	+49	57	1.2k	16mo
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. A documentation question rather than an analytical one. I have a…	+121	139	31k	16mo
Coming back to: Column chemistry choices for a 40-residue peptide Analytics › HPLC & UHPLC peak integration system suitability gradient method data table On the subject in the title: Column chemistry choices for a 40-residue peptide Working notes rather than a conclusion. Posting the method first, because I know what the first three replies will otherwise be.…		2	43k	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. Working through the identity arithmetic and I would like it checked.…	+67	76	21k	16mo
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. I would like to understand what this number means…	+128	148	47k	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
Why mass spectrometry cannot tell you about an epimer Analytics › Mass spectrometry LC-MS mass error (ppm) high-resolution MS charge states Why mass spectrometry cannot tell you about an epimer 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…	+75	82	4k	17mo
Specification in the result column: why that is a meaningful error — the long version Analytics › COA interpretation batch & lot numbers documentation quality certificate of analysis reference standards Specification in the result column: why that is a meaningful error — 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…	+14	18	12k	17mo
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. Working through the identity arithmetic and I would like it checked.…	+12	16	7.5k	17mo
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. Working through the identity arithmetic and I would like it checked.…	+121	129	25k	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. Posting the method first, because I know what the first…	+15	19	671	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? Posting the method first, because I know what the first three replies will otherwise be.…		2	15k	18mo
Second pass at: Certificates issued by the seller versus by a laboratory Analytics › COA interpretation certificate of analysis amino acid analysis batch & lot numbers Second pass at: Certificates issued by the seller versus by a laboratory — setting out what I have, and where I think it stops being reliable. A documentation question rather than an analytical one. I have a…	+81	92	20k	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
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. A documentation question rather than…	+100	112	15k	19mo
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 through the identity arithmetic and I would like it checked.…	+58	63	1k	19mo
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. Posting the method first, because I know what the first three…	+116	135	42k	19mo
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. A documentation question rather than an analytical…	+149	164	36k	19mo
Why I ask for the gradient before I discuss the number Analytics › HPLC & UHPLC gradient method data table HPLC system suitability The question in the title: Why I ask for the gradient before I discuss the number I will give what I have already checked below so nobody repeats it. I would like to understand what this number means before I…	+35	39	4.9k	20mo
Relative retention time as a better inter-laboratory comparator — does this still hold? Analytics › Method validation LOD & LOQ precision & repeatability stability-indicating method recovery Solved Wiki Relative retention time as a better inter-laboratory comparator — does this still hold? I have a specific reason for asking rather than idle curiosity, and the context is below. A documentation question…	+11	15	21k	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. Posting the method first, because I know what the first three replies will otherwise be.…	+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
Coming back to: What consumer-accessible tests can and cannot determine Analytics › Home & field testing third-party testing documentation quality LOD & LOQ ELISA Asking directly, because I could not find a straight answer: What consumer-accessible tests can and cannot determine Posting the method first, because I know what the first three replies will otherwise be.…	+4	8	25k	22mo
Gradient steepness and apparent purity: a worked comparison Analytics › HPLC & UHPLC data table UV & DAD detection peak integration HPLC On the subject in the title: Gradient steepness and apparent purity: a worked comparison Working notes rather than a conclusion. A documentation question rather than an analytical one. I have a certificate in…		2	51k	22mo
A rising related-substance total over six months: degradation or method drift? Analytics › Impurities & related substances data table endotoxin testing HPLC Closed Asking directly, because I could not find a straight answer: A rising related-substance total over six months: degradation or method drift? Posting the method first, because I know what the first three…	+37	42	37k	23mo
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. Working through the identity arithmetic and I would like…	+54	58	1.2k	23mo
Coming back to: Purity assay versus content assay: two different numbers Analytics › COA interpretation certificate of analysis reference standards batch & lot numbers Under review Purity assay versus content assay: two different numbers — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I repeat it anywhere. A…	+71	77	31k	23mo