Monitoring of trace organic compounds is the foundation stone of most national strategies aiming to improve surface water quality and to maintain drinking water safety. These compounds originate from human activities and enter the aquatic environment through various pathways, urban or agricultural run-off or wastewater treatment plants. Adverse effects of trace organic compounds on the aquatic environment cannot be ruled out. In order to provide information about the occurrence and concentration of trace organic compounds in water bodies, monitoring and screening programmes have been implemented [1,2]. Therefore detection techniques, namely gas and liquid chromatography (LC), both coupled to highly sensitive mass spectrometry (MS) are well established worldwide. While the use of gas chromatography is restricted to volatile compounds, which represent only a minor fraction of the compounds detectable in environmental water samples, LC-MS techniques are now recognised as the leading techniques in water monitoring. For the separation of compounds in LC-MS, reversed phase chromatography (RPLC) is mainly applied. RPLC is likely to be the best established, most robust and best understood separation technique in this fi eld. Most known trace organic compounds of interest can be separated and detected by RPLCMS. But interestingly, a huge number of compounds from water samples show little or no retention in RPLC and can therefore hardly be detected by MS. Based on its characteristics, RPLC is suitable for the separation of medium polar to nonpolar (i.e. hydrophobic) compounds [3]. Since retention increases in RPLC with increasing hydrophobicity, low retention indicates high compound polarity. In order to access this compound polarity range, RP stationary phases are continuously modifi ed. Although polar-endcapping and polar-embedded RP phases have improved the polarity range of reversed phases, very polar compounds still cannot be separated by RP.