purity

Something I keep coming back to: purity — 6 things I got wrong before I got it right. My first certificate had a compound name, a percentage and a logo. I thought that…

The title is the whole question — help me understand LC-MS, I have read the wiki twice — but here is why I am asking. Area percent is the integrated area of your peak…

the related substances advice in here is 3 years out of date. It is the sort of thing everyone half-believes and nobody writes down. 3 years — those are the numbers,…

Slightly embarrassed to be asking this, but: can we stop arguing about purity until somebody posts a number. My first certificate had a compound name, a percentage and…

SSA vs TFC on the same compound, same month — both cleared 97.5%. I will put the method line and the batch identifier up front because that is what makes this…

Numbers in the title, numbers in the post. TFC vs SSA on the same compound, same month — both cleared 98.0%. Figures up front so nobody has to dig: 98.0%. Sent one vial…

the method development rule is doing its job and people should stop complaining. Disagreement welcome, but bring a concrete alternative wording. Why two honest labs…

Genuine question, and the title is the question: why does nobody talk about gradient. UV response is not uniform across species. At 214nm you are looking at the peptide…

how much of what we believe about HPLC actually comes from gradient threads, and I want the answer with the reasoning attached rather than just the conclusion. Gave the…

Question in the title, detail here: genuine question about HPLC that I am slightly embarrassed to ask. MKM sent me the column, the gradient and the theoretical mass…

Title says it — KP cagri — VendorInvestigate came back 98.1% against a claimed 97.5% — so here is the boring supporting detail that makes it worth anything. 98.1% and…

genuine question about COA that I am slightly embarrassed to ask. I am not trying to be the "source?" guy. I would just like a source. The four things a certificate…

the certificate of analysis question that gets asked weekly, answered properly, which sounds obvious until you try to state the evidence for it. The PDF creation date…

is 99.1% actually fine or am I being sold a rounding error. That is the headline. The document, the batch and the service are below so you can argue with the method…

Question in the title, detail here: can we stop arguing about batch until somebody posts a number. Area percent is the peak area of your compound over the total…

HJ cagri — Janoshik came back 97.5% against a claimed 97.0%, and before anyone asks: same batch throughout, single submission, no cherry-picking between services. The…

Posting this because the title is the whole finding — HJ vs QYB on the same compound, same month — both cleared 97.0% — and a number without its method is a rumour.…

Trying to get a straight answer on this: someone explain HPLC to me like I have not read a paper in years. The system suitability argument, since it comes up whenever…

Explainer, as requested in the last thread: test results are not what most of this community thinks it is. On inter-lab disagreement, which generates more heat here…

integration — 22 things I got wrong before I got it right. It is the sort of thing everyone half-believes and nobody writes down. Resolution between two peaks depends…

Genuine question, and the title is the question: how much of what we believe about gradient actually comes from purity threads. UV response is not uniform across…

Posting this as a discussion rather than a claim: the water content question that gets asked weekly, answered properly. Why the same vial can honestly produce three…

unpopular opinion: most of what gets said here about certificate of analysis is guesswork — a position I have arrived at slowly and would like tested. LC-MS gives you…

purity — 19 things I got wrong before I got it right, which sounds obvious until you try to state the evidence for it. Area percent is the integrated area of your peak…

The claim in the title is exactly the claim I am making: TFC BPC — Janoshik came back 98.3% against a claimed 98.0%. Nothing implied beyond it. Since the title puts…