negative intercept and no peaks

[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

[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.

[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

[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