Recovery of IS in online SPE

[Anna01]

Hi!

A quick basic question...

When working with (online) SPE should the AUC of the internal standard be pretty much identical in biological matrices and H2O matrices?

I am doing LC-MS/MS, and my IS is about 80% in biological matrix compared to IS added to H2O.

Is ion suppression the most likely explanation? Or may the SPE column prove different recoveries in different matrices? (All analytes behave the same)

I am trying to improve my sample cleanup....

Thanks,

Anna

[Uwe Neue]

The SPE column should not give you any different retention with and without matrix. To make sure, you can check a blank (=IS in water) after your first few runs. The most likely problem with the matrix is ion suppression.