Molecularly imprinted polymeric sorbents

The sorbents that are most frequently used in environmental analysis are Cig-silica based sorbents, polymeric sorbents (usually styrenedivinilbenzene) and graphitized carbon. In order to increase the selectivity of these sorbents, immunosorbents (35, 36) have been developed and used with good results, while recently, molecularly imprinted polymers have started be to used (35, 36). 

Another example of new sorbents is the molecular imprinted polymers (MIP) from the work of Siemann and co-workers (1996). They synthesized a methacrylic acid-ethylene glycol dimethacrylate copolymer with atrazine as an imprint molecule. Imprint synthesis entails polymerization around an imprint species with monomers that are selected for their ability to form specific and definable interactions with the imprint molecule. The atrazine is chemically removed from the polymer leaving holes or cavities. The cavities are formed in the polymer matrix whose size and shape are complementary to that of the imprint molecule (Siemann et al., 1996). These recognition sites enable the polymer to rebind the imprint species selectively from a mixture of closely related compounds, in many instances with binding affinities approaching those demonstrated by antigen-antibody systems. 

One of the most important features of molecular imprinting is to provide a means for creating robust polymeric recognition materials with predetermined ligand selectivity [5-7]. Thus, the main application of MIPs turned out to be in the field of separation sciences, as stationary phases in (electro)chromatographic analysis and chiral separations and as selective sorbents in solid phase... 

Computational methods were employed in efforts to elucidate physical mechanisms underlying the ligand selectivity of polymeric sorbents produced through the molecular imprinting of 17-/3-estradiol [Olsson et al., 2013], A series of comprehensive MD simulations was performed on the prepolymerization systems. The results from the studies highlight the role of the cross-linker and the importance of the interplay between functionalities of the various monomers employed in template complexation. 

SPE is an exhaustive and almost solvent-free sample preparation technique. Typically, a tube is filled with a sorbent, which can be porous particles or a polymerized monolith. Various interactions are used to extract analytes from complex samples. Many of the commercially available SPE systems are for single use, but some, like RAM (restricted access materials) and MIP (molecular imprinted polymers), are typically obtained as reusable extraction devices. As will be discussed in detail, the extraction sorbents mainly function as normal phase, reversed phase, cation exchange, anion exchange, or a combination of these. 

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