Atrazine-imprinted polymers selectivity

Sergeyeva TA, Piletsky SA, Brovko AA, Slinchenko EA, Sergeeva LM, El skaya AV. Selective recognition of atrazine by molecularly imprinted polymer membranes. Development of conductometric sensor for herbicides detection. Anal Chim Acta 1999 392 105-111. 

The first work in this field was probably that of Piletsky et al. [84] that described a competitive FILA for the analysis of triazine using the fluorescent derivative 5-[(4,6-dichlorotriazin-2-yl)amino]fluorescein. The fluorescence of the supernatant after incubation was proportional to the triazine concentration and the assay was selective to triazine over atrazine and simazine. The same fluorescent triazine derivative was applied to competitive assays using atrazine-imprinted films [70]. To this end an oxidative polymerization was performed in the presence of the template, the monomer(s) 3-thiopheneboronic acid (TBA) or mixtures of 3-amino-phenylboronic acid (APBA) and TBA (10 1) in ethanol-water (1 1 v/v) where the template is more soluble. The polymers were grafted onto the surface of polystyrene microplates. The poly-TBA polymers yielded a detection limit of 8 pM atrazine whereas for the poly-TBA-APBA plates it was lowered to 0.7 pM after 5 h of incubation. However, a 10-20% decrease in the polymer affinity was observed after 2 months. 

Siemann, M., L.I. Andersson, and K. Mosbach (1996). Selective recognition of the herbicide atrazine by noncovalent molecularly imprinted polymers. J. Agric. Food Chem., 44 141-145. 

Fig. 13.10. Selectivity of atrazine-imprinted (A) and ametryn-imprinted (B) polymers.

Another example of new sorbents is the molecular imprinted polymers (MIP) from the work of Siemann and co-workers (1996). They synthesized a methacrylic acid-ethylene glycol dimethacrylate copolymer with atrazine as an imprint molecule. Imprint synthesis entails polymerization around an imprint species with monomers that are selected for their ability to form specific and definable interactions with the imprint molecule. The atrazine is chemically removed from the polymer leaving holes or cavities. The cavities are formed in the polymer matrix whose size and shape are complementary to that of the imprint molecule (Siemann et al., 1996). These recognition sites enable the polymer to rebind the imprint species selectively from a mixture of closely related compounds, in many instances with binding affinities approaching those demonstrated by antigen-antibody systems. 

High selectivity can be obtained by imprinting polymers with neutral molecules.80 In this process, a cross-linked polymer is prepared in the presence of a template. Then the template is removed by solvent extraction. The extracted polymer is then used to pick up the template molecules from other sources. Among the examples in the literature are some that deal with atrazine (an herbicide), cholesterol, other sterols, dipeptides, TV-acetyltryptophane resolution (L-isomer favored by a factor of 6), adenine, and barbiturates.81 The polymerizations in the first two examples, are shown in (7.16) (The cross-linking comonomer with the cholesterol-containing monomer was ethylenebis-methacrylate. The cholesterol was cleaved from the polymer with sodium hydroxide in methanol.)... 

Umpleby, R.J. II Bode, M. Shimizu, K.D. Measurement of the continuous distribution of binding sites in molecularly imprinted polymers. Analyst 2000,125, 1261-1265. Matsui, J. Doblhoffdier, O. Takeuchi, T. Atrazine-selective polymer prepared by molecular imprinting technique. Chem. Lett. 1995, 6, 489. 

MATSUI J, MIYOSHIY, doblhoff-dier o and TAKEUCHIT (1995), A molecularly imprinted synthetic polymer receptor selective for atrazine , Anal Chem,... 

In Piletsky s latest work, free-standing membranes are formed by polymerisation between two glass slides, with oligourethane acrylate being incorporated in the polymer mixture to lend extra flexibility [94,95]. Using atrazine again as the imprinted species, a detection limit for atrazine of 5 nM and 20-fold selectivity over simazine are reported. 

Applications. An example of practical approach based on polymer-imprinted materials is the development of biosensors for the detection of the herbicides atrazine [87] and 2,4-dichlorophenoxyacetic acid (2,4-D) [88]. The first one is based on conductimetric detection and it uses an atrazine selective polymeric matrix generated from triethylene glycol dimethacrylate... 

With regard to substrate-selective sensors with pre-organized cavities, impressive advances have been made in molecular imprinting [55-57]. The discovery of MIP-membrane electro conductivity was an interesting issue, which actually led to the appearance of the earliest MIP sensors [58,59]. It was shown that the membrane electroconductivity could be a function of the interaction between MIP-membrane and ligand (i.e., imprint species) (Fig. 5). An increase in the ligand concentration would result in an enhancement of membrane conductivity. With the same level of concentration, a maximal electro conductivity with the imprint species could be achieved. In addition, it has also been confirmed that polymers imprinted with amino acids, nucleosides, atrazines, sialic acids, or cholesterols can show similar features if coupled with the appropriate transducer [60-64], In particular, molecular imprinting is presently probably the only choice when no suit-... 

Matsui, J. Doblhoff-Dier, O. Takeuchi, T. Atrazine-selective polymer prepared by molecular imprinting technique. Chem. Lett. 1995, 6, 489. 

---