Chromatography Forum

Dear group members,

I am developing the bioanalytical method for theophylline molecule on lc/ms/ms. I m facing problem with the peaks in blank plama. Even am getting 10 to 11 thousand area in blank. My mobile phase composition is ACN:0.1%HCOOH. flow rate adjusting from 0.8 to 1.0ml. pka of the molecule is 8.66. Am trying with different moble phase composition. My extraction method is LLE. Am using Tertiary butyl methyl ether (tried with diff solvents). only problem facing with the area in the blanks. Am not understanding why peaks are coming in the blank plasma.

Am i following the correct method ?
is there any method to over come peaks in blanks?
pl suggest me the right way to develop my method.

looking forward for your reply,
regards

chari

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If these peaks have the correct MS my suggestion is that you search for "carryover" (or "carry-over") in this forum.

Have you excluded the presence of caffeine and its metabolites in the blank plasma?
Depending on the uses analytical columns and the monitored ions (fragments), you can get considerable interferences with theophylline.

Caffeine/Theophylline will be hard to get rid of in any biological matrix. You'll be hardpressed to find these types of matrices without some type of trace level.