Ametryn-imprinted polymers

Fig. 13.9. Binding of the original template species in atrazine-imprinted (A) and ametryn-imprinted (B) polymers.

Using the above-described automated system, several functional monomers have been screened for the development of molecularly imprinted polymers for the herbicides atrazine and ametryn [54]. According to the results, MAA appears to be more effective for developing the affinity in the atrazine-imprinted polymers. In contrast, 2-(trifluo-romethyl)acrylic acid is more effective for ametryn imprinting. 

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. 

Takeuchi and co-workers (18) coupled combinatorial techniques with molecular imprinted polymers to develop sensors for triazine herbicides. The library consisted of a 7 x 7 array containing different fractions of monomers methacrylic acid (MAA) and 2-(trifluoromethyl)acrylic acid (TFMAA) with constant concentrations of the imprint molecules ametryn or atrazine. After UV-initiated polymerization, the products from the sensor library were characterized by HPLC measurement of herbicide concentration. The receptor efficiency was observed to vary with monomer type the atrazine receptor efficiency increased with MAA composition and the ametryn receptor was enhanced by increased fractions of TFMAA. Although only monomer concentration was varied in the hbraries, the authors conclude that the CM synthetic approach would be usefiil in analyzing other variables such as solvent, cross-linking agent, and polymerization conditions to produce optimum molecularly imprinted polymer sensors. 

MAA and the stronger acid TFM as functional monomers.5 The polymers were different in the used molar ratio of total functional monomer to template and the molar ratio of MAA to TFM. The polymer library was subjected to a competitive binding experiment by incubating each member with an equimolar mixture of ametryn and atrazine. The templates exhibited a different preference for the two monomers. Although the more weakly basic chlorotriazine prefered the weaker acid MAA, ametryn was best imprinted using TFM as functional monomer. 

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