Matrix effects (ME) can have a considerable effect on the quantitative bioanalytical LC-MS/MS method results. Therefore it is often required to minimize them in order to increase method reliability. Hydrophilic interaction liquid chromatography (HILIC) has been referenced as one of possible approaches how to reduce the matrix effects. There is a lack of experimental research results which can confirm and give an experimental evidence of a positive effect of HILIC on the reduction of the ME. The aim of presented work was to compare matrix effects in the method development using HILIC mode or reversed phase chromatography (RP mode) and to highlight the advantages and drawbacks of each chromatographic mode.
Matrix effects were evaluated using spiked serum samples after solid phase extraction and protein precipitation prior to ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). Chromatography was performed in both HILIC and RP modes. The influence of the matrix effects on the signal response was assessed using a set of 34 compounds of pharmaceutical interest and post-extraction addition approach.
HILIC demonstrated some potential to reduce the occurrence of matrix effects. However, this only applied, when more thorough sample pre-treatment procedure was employed.

Acknowledgement
The authors gratefully acknowledge the financial support of the Charles University in Prague, project UNCE No. 204026/2012. This publication is also a result of the project implementation: „Support of establishment, development, and mobility of quality research teams at the Charles University“, project number CZ.1.07/2.3.00/30.0022, supported by The Education for Competitiveness Operational Programme (ECOP) and co-financed by the European Social Fund and the state budget of the Czech Republic.