## 3 Applications in Food Safety
### Preparative Solutions  
Food is usually considered a rather complicated matrix in the development of analytical methods. New methods and techniques should be developed to monitor the presence of residues and contaminants in food. Generally, the analysis of this kind of sample requires a pretreatment step to reduce matrix content and interfering compounds that would compromise the accuracy of the results. With this regard, monoliths possess a great potential for the clean-up and preparation of complex mixtures. Several porous monolith microextraction formats, including for example in-tube solid-phase microextractions, stir bar sorptive extraction (SBSE) and spin columns, have been published in the last decade, as may be appreciated in the existing reviews on the topic [16, 63, 64]. Microextraction techniques using porous monoliths offer several advantages, including miniaturization, high-throughput performance and on-line coupling with analytical instruments. Additionally, they may be considered as solvent-free and portable. This part of the review is focused on the methods of sample preparation for the determination of residues and contaminants in food matrices by monolith-based techniques. To overcome the disadvantages of bulk polymers (crushing, grounding, sieving, irregular particle size and shape, _etc._), monolithic polymers prepared by _in situ_ polymerization directly inside appropriate supports are becoming more frequent. The most common polymer monolith microextraction (PMME) procedure is performed with an extraction device composed of a regular plastic syringe, a monolithic capillary tube and a plastic pinhead [39]. Furthermore, elastic monolithic fiber can be synthetized inside glass capillaries (eliminated after polymerization) to obtain monolithic fibers for solid phase microextraction, as demonstrated by [PERSON] _et al._ in their recent method for the determination (SPME) of benzimidazole residues in milk and honey [53]. Another example is the very recent method developed by [PERSON] _et al._ for solid-phase microextraction of Sudan dyes in tomato sauce and egg yolk [56]. The SPME was performed with monolithic fibers based on dual functional monomers, enabling low limits of detection in both matrices with high precision and satisfactory recoveries. A graphene-modified monolithic column was successfully utilized for purification and enrichment of four pesticides in fruit and vegetable samples. Compared with direct HPLC analysis and preconcentration with unmodified monolith, the incorporation of graphene into the monolith increased the enrichment capacity for the analytes [49]. Spin-columns offer the possibility of developing miniaturized versions of SPE extractions. The columns can be packed with conventional SPE particles, but also with monolithic materials. In these columns, a monolithic disk is packed into a spin column, and the operations (sample loading, washing and elution of the target compounds) are only carried out by centrifugation. In addition, many samples can be processed simultaneously. This simple method requires a low elution volume and does not require solvent evaporation. The spin-column technique has been used to extract various analytes in different matrices, mainly for toxicological analysis of human specimens (urine and serum) [65, 66, 67]. Very few examples of the application of these devices in the analysis of food can be found in the literature of the last five years, basically due to the complex characteristics of edible matrices. [PERSON] used a commercial silica spin mini-column (MonoSpin(r)) to extract cyromazine, an insecticide, and its metabolite, melamine, in bovine milk [36]. The author described the method as \"ultra-safe, idiot-proof and inexpensive\", as well as solvent-free, all of them clear positive aspects of this spin-columns. Pipette tip extraction is another miniaturization option for sample preparation, and some commercially manufactured pipette tip-assembled monoliths are available on the market [65].