purity

help me understand PeptideMeter, I have read the wiki twice — that is what I am asking, and I have already read the wiki twice. Date of analysis anchors the result to a…

Trying to get a straight answer on this: does gradient actually matter or is it forum lore at this point. A shoulder that does not baseline-resolve cannot be quantified…

the Janoshik thing finally clicked for me and I want to write it down, and I am aware this is a minority view on this board. Fourth lot from the same supplier in the…

Trying to get a straight answer on this: below spec — what am I missing here. Chain of custody is why member-funded testing is worth more than a supplied certificate:…

three years of method development threads, summarised so you do not have to read them. Making the case below, and I expect to lose some of it in the comments. Started…

three years of gradient threads, summarised so you do not have to read them, which sounds obvious until you try to state the evidence for it. Carryover from a previous…

we are measuring method development at the wrong time and calling it noise. I have gone back and forth on this for months. Why two honest labs report different numbers…

three years of PeptideMeter threads, summarised so you do not have to read them. It is the sort of thing everyone half-believes and nobody writes down. Inter-lab…

Right: QYB BPC — Medutest came back 99.2% against a claimed 99.0%. I paid for this one myself, nobody sent me anything, and the receipts are in the comments. The…

the LC-MS question that gets asked weekly, answered properly, which sounds obvious until you try to state the evidence for it. WWB sent me the column, the gradient and…

WWB BPC — Medutest came back 99.4% against a claimed 98.5%. I will put the method line and the batch identifier up front because that is what makes this checkable. The…

Asking properly rather than in a comment on somebody else’s thread: someone explain batch to me like I have not read a paper in years. Chain of custody is why…

unpopular opinion: most of what gets said here about test results are guesswork. Change my mind, genuinely — I have no stake in being right about this. How to build a…

Putting this to the board: proposal — a flair for batch posts. Why the same vial can honestly produce three different numbers. Purity by area percent is relative to…

LC-MS confirmed identity but the UV purity is 94%. now what, and before anyone asks: same batch throughout, single submission, no cherry-picking between services. The…

the batch rule is doing its job and people should stop complaining. Short post, long comment section, probably. Area percent is the peak area of your compound over the…

certificate of analysis is doing more work than we give it credit for. Change my mind, genuinely — I have no stake in being right about this. How to ask for a batch…

LC-MS is doing more work than we give it credit for, and I am aware this is a minority view on this board. Why two honest labs report different numbers on the same…

purity — 3 things I got wrong before I got it right. Not a hot take, just something I have not seen said plainly here. Net peptide content is the fraction of the powder…

three years of related substances threads, summarised so you do not have to read them, and I am aware this is a minority view on this board. UV at 214nm sees the…

reading gradient threads from 2024 and half of it aged badly. It is the sort of thing everyone half-believes and nobody writes down. Resolution between two peaks…

Posting this as a discussion rather than a claim: the related substances thing finally clicked for me and I want to write it down. The document I was worried about…

Medutest — 8 things I got wrong before I got it right, and I am aware this is a minority view on this board. What a result posted here is actually worth, and how to…

proposal — a flair for integration posts. Comments open, and the wording is genuinely up for discussion. UV response is not uniform across species. At 214nm you are…