Monitoring of environmental samples is usually restricted to known or suspected compounds or compound classes (“target analysis”) for which specific analytical methods have been developed and optimized. Identification of unknown compounds (“nontarget analysis”) appears to be much more difficult. In this case, sample extraction, isolation, and separation must take into account the very different (and a prori unknown) physical and chemical properties of the individual organic compounds, and the instrumental method must have high separation efficiency and provide optimum structural information.