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negative intercept and no peaks
Posted: Thu Mar 23, 2017 1:43 am
by aya
hello every one . IM Still a beginner in lcmsms . I tried to measure my drug sunitinib samples in mice plasma and used an internal stranded verapamil 50nM and made a calibration standreds from 1nM to 3000nM but the problem is in some samples I GOT NO peaks and also the intercept was negative so please can you help me in addressing the problem
Re: negative intercept and no peaks
Posted: Thu Mar 23, 2017 7:33 am
by Rndirk
You'll have to post more details or we just have to guess.
It seems you have 2 different problems: a calibration problem and a sample preparation problem.
First get your calibration right. This should be the easy part.
Re: negative intercept and no peaks
Posted: Sat Mar 25, 2017 1:16 pm
by Arne
I agree with RnDirk, but a negative intercept indicates that you might be hitting the S/N limit of your method.
Think about it this way: There needs to be a certain amount of material present to give a peak at all. All concentrations below that amount will give 0 peak area.
Also: 1 - 3000 nM is a very wide concentration range for LCMS. it is unlikely that you will have good linearity over such a a broad range. See if the response factors are equal over the range (area/concentration).
Good Luck!
Arne
Re: negative intercept and no peaks
Posted: Mon Mar 27, 2017 12:44 am
by aya
thank you very much for every one reply . Im sorry i tried to upload my excel file but i couldn't Im trying to learn as much as possible . thank you