In parallel to a long lasting search for universal multi-purpose sorbents, the area of solid phase extraction (SPE) is recently experiencing a rapid development of new types of tailor-made class specific or compound-specific sorbents which are designed to respond to the increasing demand for selectivity and efficiency in sample clean-up prior to quantification. An important issue here is the enrichment and clean-up of complex samples, such as environmental waters, sediments, biofluids and foodstuffs prior to detection. This because the analyte is often present in low concentration in a complex mixture of similar compounds and therefore needs to be isolated and enriched in order to be detected by standard analytical techniques.