Molecularly imprinted polymers analysis methods

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. 

Boyd B, Bjdrk H, Billing J, Shimelis O, Axelsson S, Leonora M, Yiknaz E, Development of an improved method for trace analysis of chloramphenicol using molecularly imprinted polymers, J. Chromatogr. A 2007 1174 63-71. 

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... 

In the second, more selective, approach a class-specific extraction with molecular imprinted polymers (MIPs) can be used [43,44] however, their use in environmental analysis has been rarely reported and so far limited to pesticide analysis. For example, Turiel et al. [45] developed a method for group-selective extraction of chlorotriazines and methylyhiotyrizines and their TPs in soils, obtaining recoveries higher than 94% for chlorotriazines and 39% for prometryn. Similarly, in the study of Chapuis et al. [46], the ametryn MIP was shown to be highly class-selective for triazines and their degradation products and was appUed to the clean-up of soil extracts. 

Other SPME-IMS methods that have been reported for application to pharmaceutical or related samples include those for analysis of ephedrine in urine, meth-amphetamines in human serum, and captopril in human plasma and pharmaceutical preparations. In a method similar to SPME-IMS, testosterone was collected with a molecular imprinted polymer from urine and desorbed into an IMS. The method was validated with HPLC and determined to have a detection limit of 0.9 ng/mL with a linear dynamic range from 10 to 250 ng/mL. ... 

The growing interest in secondary metabolites of plants leads to the requirement of the development on analytical method for the secondary product analysis. Chromatographic procedures for the determination of alkaloids have been well established. Based on the literatures published in past years, further improvement of the current methods for the analysis of Catharanthus alkaloids are needed [4]. Besides, the chemical complexity and unique bisindole alkaloid structure of the aforementioned molecules hindered their laboratorial synthesis. The isolation of VLB and VCR is laborious and costly, mainly due to their low contents in the plant and coexistence in a large number of other alkaloids [5]. Therefore, it is important for separation, identihcation, and quantiflcation of these Catharanthus alkaloids. The methods of extraction and purification were focused on liquid-liquid extraction, solid-phase extraction, supercritical fluid extraction (SFE), and molecularly imprinted polymers (MlPs)-based extraction. For separation, GC is not suitable for the bisindole alkaloids due to their high boiling point. The major methods for analysis of Catharanthus alkaloids are liquid chromatography (LC) and capillary electrophoresis (CE). 

Extraction and sample preparation are of importance in plant analysis. Clinic and forensic analyses usually rely on appropriate sample preparation to achieve a sufficiently low limit of detection. The pretreatment procedure before the chromatographic measurement must ensure exhaustive extraction of the analyte and removal of matrix that may interfere with analysis. Sample preparation methods for analysis of Catharanthus alkaloids include liquid-liquid extraction (LEE), supercritical fluid extraction (SEE), and molecularly imprinted polymers (MlPs)-based extraction. 

R. Weiss, M. Freudenchuss, R. Krska and B. Mizaikoff, Improving methods of analysis for mycotoxins Molecularly imprinted polymers for deoxynivalenol and zearalenone. Food Additiv. Contamin., 20 (4) 386-395,2003. 

In this chapter, all the processes of the molecular imprinting reaction (from the design of reaction systems to the analysis of resultant polymers) are described, so that the reader can form a clear and comprehensive mental picture of this elegant method. Non-covalent imprinting for the preparation of polymeric receptors towards atrazine (a herbicide) is taken as a typical example (Fig. 6.1). 

We believe that in the near future, the use of computational methods in conjunction with spectroscopic techniques and thermodynamic considerations should allow the in silico simulation to be used broadly for the analysis of the influence of polymerization conditions (solvent, cross-linker, temperature) on the performance of imprinted polymers, for optimization of the monomer composition and for tailoring polymer performance for specific applications. The computational approach described here represents a first step towards the truly rational design (tailoring) of MlPs and prediction of polymer properties. Nonetheless, improvements in our capacity to predict polymer performance should be benefited through the combination of molecular modeling, further physical characterization of the imprinting process, and combinatorial strategies (Chapter 8). 

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