Nicotine-imprinted polymers

In a further application of MI-SPE, theophylline could be separated from the structurally related caffeine by combining the specific extraction with pulsed elution, resulting in sharp baseline-separated peaks, which on the other hand was not possible when a theophylline imprinted polymer was used as stationary phase for HPLC. A detection limit of 120 ng mb1 was obtained, corresponding to a mass detection limit of only 2.4 ng [45]. This combination of techniques was also used for the determination of nicotine in tobacco. Nicotine is the main alkaloid in tobacco and is the focus of intensive HPLC or GC analyses due to its health risk to active and passive consumers. However, HPLC- and GC-techniques are time-consuming as well as expensive, due to the necessary pre-purification steps required because the sample matrices typically contain many other organic compounds besides nicotine. However, a simple pre-concentration step based on MI-SPE did allow faster determination of nicotine in tobacco samples. Mullett et al. obtained a detection limit of 1.8 jig ml 1 and a mass detection limit of 8.45 ng [95]. All these examples demonstrate the high potential of MI-SPE to become a broadly applicable sample pre-purification tool. 

One difficulty which appears to remain to this day is the commercialisation of molecularly imprinted polymers. Although no molecularly imprinted silica product ever reached the market, at least two patents, apparently on molecular imprinting [27], were held by the group of Patrikeev [62,63]. That some commercial interest existed is also confirmed by the fact that Merck patented a nicotine filter invented by Erlenmeyer [64], consisting of nicotine imprinted silica, able to adsorb 10.7% more nicotine than non-imprinted silica. The material was intended for use in cigarette filters. 

Luis, A., Ruela, M., Flguelredo, E. C., Pereira, G. R. (2014). Molecularly imprinted polymers as nicotine transdermal delivery systems, Chem. Ena. L 248,1-8. 

Matsui, J. Takeuchi, T. A molecularly imprinted polymer rod as nicotine-selective affinity media prepared with 2-(trifluoromethyl)acrylic add. Anal. Comm. 1997, 34 (7), 199-200. 

An (-)-Ephedrine voltammetric sensor prepared through the immobilization of an MIP imprinted polymer for ephedrine in the range of 0.5-3 mM [426], and the MIP-coated gold electrode modified by chitosan-platinum nanoparticles (CS-PtNPs) and graphene-gold nanoparticles (GR-AuNPs) nanocomposites for the determination of erythromycin are other examples of the application of MIPs for the analysis of pharmaceutical species. The latter report used erythromycin as template and 2-mercapto-nicotinic acid functional monomers and yielded a linear response in the range of 7.0 x 10 -9.0 X 10 M and a detection limit of 2.3 x 10 M [378]. 

A.L.M. Ruela, E.C. Figueiredo, and G.R. Pereira, Molecularly imprinted polymers as nicotine transdermal dehvery systems, Chem. Engin. J., 248 1-8,2014. 

Molecular imprinting has been used to devise a chemosensor for L-nicotine (Table 6) [178]. For that, poly(methacrylic acid) (PMA) beads, imprinted with the L-nicotine template in chloroform, were incorporated in a film of the conjugated polymer, OCiC10-PPV. EIS has then been utilized for the L-nicotine determination in the 1-10 nM concentration range. This MIP chemosensor showed predominant affinity towards L-nicotine over a structurally related L-nicotine metabolite, L-cotinine. Similarly, the polydopamine-imprinted film prepared by electropolymerization in the phosphate buffer (pH = 7.4) has been used to devise a chemosensor for L-nicotine with LOD of 0.5 pM (Table 6) [106]. This LOD is still much higher than that reported for other L-nicotine determination methods based on MIPs, such as SPE combined with differential pulsed elution, which was 6 nM [31]. 

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