Electrochemically solid phase microextraction based on molecularly imprinted polymer-carbon nanotubes composite

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Electrochemically controlled solid phase microextraction (EC-SPME) was proposed as an alternative to classic SPME for the enhanced isolation of ionic or ionizable compounds (1). EC-SPME is based on the application of a potential difference between the sample and the extracting phase, and therefore special conducting coatings, such as those based on polypyrrole, are required.

Classic SPME coatings lack of extraction selectivity due to their hydrophobic nature. As we've mentioned in previous posts (I, II), molecularly imprinted polymers enhance the recognition selectivity through hydrogen-bonds, ionic interaction, and size-shape matching. In a recent article, published in Analytica Chimica Acta, Liu et al. have proposed a nanocomposite as special coating in EC-SPME for the selective extraction of fluoroquinolones from water samples (2). The nanocomposite is based on the combination of carbon nanotubes (CNTs), which increase the stability and mechanical strength of the fiber, and a conducting molecularly imprinted polymer which improves the selectivity.

The synthesis of the nanocomposite consists of different steps. First of all, a layer of multiwalled carbon nanotubes is deposited in a platinum wire by an electrochemical process which involves the application of an electrical potential difference between two electrodes immersed in a suspension of carboxylic CNTs. In a subsequent step, the MIP layer is prepared by the electropolymerization of pyrrole in the presence of ofloxacin which is used as template molecule. The MIP nanocomposite presents a high porous structure compared with that synthesized in the absence of template (NIP).

Among all the involved variables, the applied electrical potential is especially interesting since it has a double effect on the extraction performance. On the one hand, it improves the extraction of the analytes but on the other hand it may produce the over-oxidation of the coating.

In the article, the readers will find some interesting information concerning the synthetic process, the optimization of the extraction procedure and the comparison between the NIP and MIP performances.


References:
(1) Electrochemically Controlled Solid-Phase Microextraction Based on Conductive Polypyrrole Films. Link to the article
(2) An electrochemically enhanced solid-phase microextraction approach based on molecularly imprinted polypyrrole/multi-walled carbon nanotubes composite coating for selective extraction of fluoroquinolones in aqueous samples. Link to the article

Related posts:
(I) Thin films of molecularly imprinted polymer for the selective extraction of proteins. Link to post
(II) Smart molecularly imprinted hydrogels for protein recognition.  Link to post

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