[Lab] 16th independent test on ERP — 97.4% on a claimed 97.0%, and the trend is the interesting part
Numbers in the title, numbers in the post. 16th independent test on ERP — 97.4% on a claimed 97.0%, and the trend is the interesting part.
Since the title puts numbers in the shop window: 97.4% and 97.0%.
Gave the same trace to two people I trust and got two integrations about a point apart. That was the most educational afternoon I have had here.
Sent the same vial to PeptideMeter and Medutest. 99.3% against a claimed 98.5%. The difference was the gradient, not the material.
Screenshot none of this. Read the whole thread, including the parts where I am told I am wrong.
- ERERP source pageShanghai ERP Biotechnology Co., Ltd. · Shanghai · 90% here, rank 18 · shop at erpbiotechnology.com →
nofollow and sponsored; nobody here is paid for it.best — the order this archive was captured in
A shoulder that does not baseline-resolve cannot be quantified honestly. You can report it as an unresolved shoulder, which is useful information, or you can develop the method until it resolves.
Area percent is the integrated area of your peak over the total integrated area at one wavelength on one gradient. Change any of those and the number changes without the sample changing.
214nm sees the peptide bond, 280nm sees the aromatics
Correction: that is a tailing factor, not a plate count. Different diagnostics for different problems.
What wavelength, and what was the gradient?
What did system suitability look like on that sequence?
Area percent is the integrated area of your peak over the total integrated area at one wavelength on one gradient.
This is the whole methodological point of the board in one line.
This is the whole methodological point of the board in one line.
Agreed. And the corollary is that the method line on a certificate is not decoration, it is the number’s provenance.
This. A shoulder that does not baseline-resolve is a question, not a quantity.
Small fix — 214nm, not 210. It matters for the comparison you are making with the other run.
reproducibility beats resolution if you only get one of them
Resolution between two peaks depends on retention, selectivity and efficiency. A shallower gradient buys retention and usually resolution, at the cost of peak width and run time.
Resolution between two peaks depends on retention, selectivity and efficiency.
Disagreeing with this bit: that spread is ordinary inter-lab variance, not a disagreement about the material.
Is that baseline drawn by the software or by hand?
a shoulder is not an impurity until you can resolve it
Trace posted without axis labels — asked for a relabelled version rather than removing it.
Yes. Retention time is a hypothesis about identity. Mass is the answer.
Do you have the mass, or only the UV trace?
That is area percent, not mass percent. The trace cannot give you the second one.
The system suitability argument, since it comes up whenever somebody posts a number without one.
Before the sample result means anything, the instrument has to be shown to be fit that day: replicate injections with an acceptable RSD on area, a tailing factor inside limits, adequate plate count, and a resolution check between the pair you care about.
None of that is exotic and all of it is routine in a laboratory that reports for a living. Its absence does not mean a number is wrong; it means the number is unanchored, and unanchored numbers should not be quoted to two decimal places on this board.
- 1Area percent is the integrated area of your peak over the total integrated…10 comments in this branch · started by u/clara_danquah
- 2reproducibility beats resolution if you only get one of them6 comments in this branch · started by u/nora_lundgren