Mixed-mode stationary phases as a complementary selectivity concept in liquid chromatography-tandem mass spectrometry-based bioanalytical assays

The importance of mixed-mode stationary phases as a complementary selectivity concept in liquid chromatography-tandem mass spectrometry to serve as an alternative separation concept for bioanalytical investigations of polar analytes are discussed. Chromatographic separation and mass spectrometry detection also play a major role in providing satisfactory analytical selectivity, which is a basic criterion for ensuring the accuracy of a method. Mass spectral interferences arising form the unintended in-source fragmentation of compounds may also seriously affect reliable determinations of target analytes in the case on coelution. Mixed-mode phases combining orthogonal separation principles offer much more optimization potential than classical RP chromatography. Various modes of gradient elution add further flexibility during method development.