Extraction techniques molecularly imprinted polymer

MSPD). Other techniques used for some specific applications are microwave-assisted and ultrasonically assisted extraction (MAE, UAE), immunoaffinity(-based) extraction (lAC), and polymer imprinted types of extraction techniques [molecularly imprinted polymer (MIP)]." ... 

B. B. Prasad, M.P. Tiwari, R. Madhuri and P.S. Sharma, Development of a highly sensitive and selective hyphenated technique (molecularly imprinted micro-solid phase extraction fiber-molecularly imprinted polymer fiber sensor) for ultratrace analysis of folic acid. Anal. Chim. Acta, 662 (1) 14-22,2010. 

The most widely employed techniques for the extraction of water samples for triazine compounds include liquid-liquid extraction (LLE), solid-phase extraction (SPE), and liquid-solid extraction (LSE). Although most reports involving SPE are off-line procedures, there is increasing interest and subsequently increasing numbers of reports regarding on-line SPE, the goal of which is to improve overall productivity and safety. To a lesser extent, solid-phase microextraction (SPME), supercritical fluid extraction (SEE), semi-permeable membrane device (SPMD), and molecularly imprinted polymer (MIP) techniques have been reported. 

Recent trends in pesticide analysis in food aims for reduced sample pretreatments or simplified methodologies (as QuEChERS approaches), the use of online purification processes, the use of new adsorbents (such as molecular imprinted polymers (MIPs) and nanomaterials) for the extraction and clean-up processes, and focused on the development of large multiresidue methods, most of them based on LC-MS/ MS. In spite of the relevant role of LC-MS/MS, GC-MS-based methods still play an important role in pesticide analysis in food. Despite the development achieved in the immunochemical approaches, the need for multi-residue methods has supported the development and use of instrumental techniques. 

There are several future trends for the development of passive sampling techniques. The first is the development of devices that can be used to monitor emerging environmental pollutants. Recently, attention has shifted from hydrophobic persistent organic pollutants to compounds with a medium-to-high polarity, for example, polar pesticides, pharmaceuticals, and personal care products.82 147148 Novel materials will need to be tested as selective receiving phases (e.g., ionic liquids, molecularly imprinted polymers, and immunoadsorbents), together with membrane materials that permit the selective diffusion of these chemicals. The sample extraction and preconcentration methods used for these devices will need to be compatible with LC-MS analytical techniques. 

Sellergren, B. (2001) Molecularly imprinted polymers in solid-phase extractions. In Lanza, F. (Ed.) Molecularly Imprinted Polymers-Man-made Mimics of Antibodies and Their Applications in Analytical Chemistrf. Techniques and Instrumentation in Analytical Chemistry, Vol. 23, Elsevier, Amsterdam, NL. 

Molecularly imprinted polymer recognition units are based upon template polymerization techniques (Haupt and Mosbach 2000). The MIP recognition units are formed in the presence of a template molecule that is later leached out or extracted, thus leaving complementary cavities embedded in the Ii nal structure of the polymer. These polymers display high chemical-binding affinity for molecules with structural similarities to the template molecule. Hence, MIPs can be used to fabricate sensors... 

The application of MIPs as the stationary phase in solid-phase extraction (SPE), often referred to as molecularly imprinted polymer solid-phase extraction (MIS P E), is a rapidly growing area [197-199]. With MISPE, highly specific enrichment of substances present at trace levels is possible. The technique has been applied to the analysis of drugs, for example, caffeine [200], scopolamine [201], naproxen [202], tetracycline [203], cholesterol [204] and local anesthetics [205], as well as environmental pollutants, exemplified by organophosphate flame retardants [206-208], triazines in soil and vegetable samples [71] and naphthalene sulfonates in river water [209]. 

Most nitroimidazole methods also incorporate further clean-up steps such as solid phase extraction (SPE). Some common phases used include Oasis Oasis MCX, Chromabond XTR, SCX, Bakerbond Silica, and MIP-SPE (molecular imprinted polymer). In addition, most methods incorporate a solvent washing step with solvents such as hexane prior to instrumental analysis for removal of non-polar material. More recent work bypassed extensive clean-up techniques such as SPE as it was felt that recent advances in MS/MS technologies and... 

A molecularly imprinted column for liquid chromatography can be used not only to separate analytes, but also to selectively extract analytes from complex samples. This technique is called on-line Molecularly Imprinted Solid Phase Extraction (on-line MISPE), and it combines the high extraction efficiency of reverse phase SPE for aqueous samples with the high selectivity of the molecular-imprinted polymers. Examples of successful selective extraction and clean-up are reported in Figs. 9 and 10. 

SBSE presents a series of advantages over the rest of extraction techniques is solvent-free (environmental friendly) could be completely automated don t requires pre-treatment of samples (reduces analytical errors) and presents greater sensitivity than SPME, reaching lower detection and quantitation limits. However, it presents two clear disadvantages compared with the other extraction techniques PDMS is the only phase commercially available to date, limiting the extraction of polar substances and a specific thermal desorption unit is required for optimize the process (Castro et al., 2008). The increase of the extraction yields for the recovery of polar compoimds could be carry out by in-site derivatization. Recently, other phases under development were referred, namely those based on the sol-gel technology, restricted access materials and molecular imprinted polymers (Prieto et al., 2010). 

A simple method was developed (Gao R. et al., 2010) to synthesize core-shell molecularly imprinted polymers for the extraction of tridosan with fast kinetics, high capacity and favorable selectivity by combining a surface molecular impainting technique with a sol-gel process based on carbon nanotubes coated with siUca... 

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. 

A. Ersoz, S.E. Ditemiz, A.A. Ozcan, A. Denizh and R. Say, Synergie between molecular imprinted polymer based on solid-phase extraction and quartz crystal microbalance technique for 8-OHdG sensing. Biosens. Bioelectron., 24 (4) 742-747, 2008. 

M. Shekarchi, M. Pourfarzib, B. Akbari-Adergani, A. Mehramizi, M. Javanbakht and R. Dinarvand, Selective extraction of lamivudine in human serum and urine using molecularly imprinted polymer technique, / Chromatogr. B, 931 50-55, 2013. 

B.B. Prasad, A. Srivastava and M.P. Tiwari, Highly selective and sensitive analysis of dopamine by molecularly imprinted stir bar sorptive extraction technique coupled with complementary molecularly imprinted polymer sensor, J. Colloid Inter/. Set, 396 234-241, 2013. 

Molecular imprinted polymers (MIPs) can be prepared according to a number of approaches that are different in the way the template is linked to the functional monomer and subsequently to the polymeric binding sites. The current technique makes use of noncovalent self-assembly of the template with functional monomers before polymerization, free radical polymerization with a cross-linking monomer, and then template extraction followed by rebinding by noncovalent interactions. The functional monomer is often methacrylic acid, the cross-linker is ethylene glycol dimethacrylate, the initiator is 2,2-azo-A,lV -to-isobutyronitrile. They are mixed with template and the mixture is reacted at elevated temperature. The resultant rigid polymer is ground into a sieved powder and the template enantiomer washed off. 

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