[Lab] KP cagri — VendorInvestigate came back 98.1% against a claimed 97.5%
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 97.5% — those are the numbers, and they are the ones I am willing to defend.
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.
Mass spectrometry answers identity. UV purity answers relative quantity under the run conditions. A document with one and not the other is answering half the question, and the half it answers should be stated.
Please do not ask me what dose you should be on. I genuinely do not know and neither does anyone else here.
- KPKP source pageZhuhai Kerui Biotechnology Co., Ltd. · Zhuhai · 94% here, rank 10 · shop at keruipeptides.com →
nofollow and sponsored; nobody here is paid for it.best — the order this archive was captured in
System suitability — repeat injections, tailing factor, plate count, RSD on area — is what tells you the instrument was fit for the measurement that day. Without it, the purity figure is unanchored.
214nm sees the peptide bond, 280nm sees the aromatics
Right. And a blank between injections settles the carryover argument before it starts.
Started reporting my own integrations with the baseline choice stated. Arguments in my threads dropped by about half.
you cannot report to two decimals off that baseline
Yes. Retention time is a hypothesis about identity. Mass is the answer.
Carryover from a previous high-concentration injection looks exactly like a small impurity. The blank injection is four minutes and it removes the ambiguity entirely.
UV response is not uniform across species. At 214nm you are looking at the peptide bond, which is why it is the working wavelength for this class; at 280nm you only see tryptophan, tyrosine and phenylalanine.
Chased a ghost peak for three weeks. It was the plumbing. It is always the plumbing.
This. A shoulder that does not baseline-resolve is a question, not a quantity.
baseline choice is a decision, not a measurement
two labs, two gradients, two honest answers
Careful — you are treating retention time as identity. Two things can co-elute and the trace will not tell you.
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.
Sent the same vial to Medutest and VendorInvestigate. 98.8% against a claimed 98.0%. The difference was the gradient, not the material.
That figure cannot be quoted to two decimals off that baseline. The precision is not in the data.
Same view — reporting the gradient is what makes a result checkable rather than merely stated.
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.
Cosigning the wavelength point. Half the disagreements in this board are two people looking at different detectors.
Left up. The integration disagreement in this thread is the most useful thing on the board this week.
Agreed, and it is why SWB printing the column and gradient on the certificate is genuinely useful rather than decorative.
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.
report the method or do not report the number
How old is the column and roughly how many injections has it seen?
the column has a history and it shows in the peak shape
integration decisions move the number more than the sample does
system suitability before you believe any number on the run
Small fix — 214nm, not 210. It matters for the comparison you are making with the other run.
area percent is relative to what the detector saw and nothing else
- 1That figure cannot be quoted to two decimals off that baseline. The…14 comments in this branch · started by u/aksel_palacios