Abstract
Molecular imprinting is a technique for making a selective binding site for a specific chemical. The technique involves building a polymeric scaffold of molecular complements containing the target molecule. Subsequent removal of the target leaves a cavity with a structural “memory” of the target. Molecularly imprinted polymers (MIPs) can be employed as selective adsorbents of specific molecules or molecular functional groups. In addition, sensors for specific molecules can be made using optical transduction through lumiphores residing in the imprinted site. We have found that the use of metal ions as chromophores can improve selectivity due to selective complex formation. The combination of molecular imprinting and spectroscopic selectivity can result in sensors that are highly sensitive and nearly immune to interferences. A weakness of conventional MIPs with regard to processing is the insolubility of crosslinked polymers. Traditional MIPs are prepared either as monoliths and ground into powders or are prepared in situ on a support. This limits the applicability of MIPs by imposing tedious or difficult processes for their inclusion in devices. The size of the particles hinders diffusion and slows response. These weaknesses could be avoided if a means were found to prepare individual macromolecules with crosslinked binding sites with soluble linear polymeric arms. This process has been made possible by controlled free radical polymerization techniques that can form pseudo-living polymers. Modern techniques of controlled free radical polymerization allow the preparation of block copolymers with potentially crosslinkable substituents in specific locations. The inclusion of crosslinkable mers proximate to the binding complex in the core of a star polymer allows the formation of molecularly imprinted macromolecules that are soluble and processable. Due to the much shorter distance for diffusion, the polymers exhibit rapid responses. This paper reviews the methods that have been employed for the trace determination of organophosphates in real world samples using MIPs.
Highlights
Organophosphate is a term that is commonly applied to pesticides and includes chemical warfare agents
The inclusion of crosslinkable mers proximate to the binding complex in the core of a star polymer allows the formation of molecularly imprinted macromolecules that are soluble and processable
We have demonstrated that many organophosphates bind to tris(β-diketonate)Eu(III) complexes with a 1:1 stoichiometry [19]
Summary
Organophosphate is a term that is commonly applied to pesticides and includes chemical warfare agents. Organophosphates interfere with nerve function by impeding the enzyme acetylcholinesterase as opposed to the organochlorines that open sodium ion channels. Due to these health hazards, many countries impose strict restrictions on the organophosphate residual limits in drinking water and food. The ability to detect such trace amounts of organophosphates is difficult and is an area of increasing concern. Imprinted polymers (MIPs) are synthetic polymers that are stable and synthesized with specific recognition sites Due to their high selectivity, MIPs have been employed for the detection of a wide range of molecules, such as amino acids [9], pesticides [10], carbohydrates [11] and nucleic acids [12]. The studies developed for detection of organophosphates by discerning their effect on the luminescence of europium (III) will be discussed
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