# Recent Advances in Extraction and Stirring Integrated Techniques
## 4 Stir Cake Sportive Extraction  
Stir cake sorptive extraction (SCSE) was first proposed in 2011 by [PERSON] et al. [41]. It is very similar to stir bar sorptive extraction but, in this case, the sorbent is a monolithic cake placed in a homemade holder with a protected iron wire (Figure 9). This configuration avoids the direct contact of the sorptive phase with the sample vessel. As a result, higher stirring rates can be used during the extraction. In addition, the life span of the monolith is increased allowing its reuse up to 300 times, while the typical reusability of a stir bar is ca. 60. Monoliths are continuous porous structures which are easily obtained by the polymerization of a monomer mixture with a porogen solvent into a given holder (capillary, spin column, pipette tip, stir cake). Their chemistry can be tailored by the proper selection of the monomers and also the porosity can be controlled during the synthetic process. Monoliths can be classified in three groups: organic, silica, and hybrid monoliths, depending on the nature of their ingredients. Their potential in separation techniques has been widely studied [42]. The preparation of the monolith-based SCSE unit is very simple [41]. The monolithic cake is synthesized and located in a cake-shaped plastic holder (see Figure 9). The holder is finally pierced by an iron wire that allows for magnetic stirring of the system. In addition, small holes can be drilled through the holder to promote the flow of the sample through the monolithic cake. Before its first use, the monolith must be conditioned with the appropriate solvents. Once conditioned, the sorptive cake is introduced in the sample for the isolation of the analytes, which are finally eluted for instrumental analysis. Different monoliths have been used in this SCSE format, with polymeric ionic liquids and organic-based polymers being the most reported in the literature. Ionic liquids (ILs) can be considered as a group of non-molecular solvents which present a melting point below 100 \({}^{\circ}\)C [43]. Ionic liquids have been extensively used in microextraction techniques, both in the solid and liquid phase formats. In recent years polymeric ionic liquids (PILs), obtained by the polymerization of IL cations, have been also proposed in this context. In comparison with the ILs, PILs exhibit higher viscosity, thermal stability, and mechanical strength which are important characteristics for sorptive phases in miniaturized solid-phase extraction techniques [44]. PILs were first proposed as an active phase in solid phase microextraction (SPME) in 2010 [45]. In 2012, [PERSON] et al. reported the first application of PILs-monolith (PILM) in SCSE for the extraction of inorganic anions from water [46]. The PILM was in situ obtained by the copolymerization of 1-allyl-3-methylimidazolium chloride (AMIC) and ethylene dimethacrylate (EDMA) providing a final structure that exhibited a strong anionic exchange capacity towards the analytes (F\({}^{-}\), Cl\({}^{-}\), Br\({}^{-}\) NO\({}_{2}\)\({}^{-}\), NO\({}_{3}\)\({}^{-}\), SO\({}_{4}\)\({}^{-}\), PO\({}_{4}\)\({}^{3}\)\({}^{-}\)). The presence of imidazolium cations in the structure was behind this capacity. Following a similar procedure, traces of antimony can be extracted from environmental water using a PILM containing 3-(1-ethyl imidazolium-3-y)propyl-methacyamido bromide (EPB) and EDMA as precursors [47]. In this specific example, the amino groups of the PILM coordinate to Sb, favoring its extraction. PILM-SCSE has also demonstrated its applicability for the pre-concentration of organic compounds. Figure 9: Device for stir cake sorptive extraction. Reproduced with permission of the Microextraction Tech blog. The selection of the monomers is crucial to obtain an adequate sensitivity and selectivity. The monolith described in [46] was also efficient for the extraction of preservatives (sorbic, benzoic, and cinnamic acids) in fruit juices and soft drinks [48].