EL TRA SITO Y LA RESIG IFICACIÓ DE SI MISMOS COMO EFECTO REPARADOR

The voltammetric behavior of 2-nitrophenol and 4-nitro- phenol using clay-modified carbon paste electrodes was explored, with montmorillonite and sepiolite as modifiers. The response of the electrode to both analytes is increased after the modification when employing differential pulse voltammetry. Accumulation of the analyte occurred only for 2-NP, offering further increase of the sensitivity. The lowest detection limit was obtained for 2-NP using AdSV on MMT-CPE with LOD 7.1·107 molL1, while for 4-NP the detection limit was 2.0·106 mol L1 using DPV on MMT-CPE.

Financial support of the Czech Ministry of Educa- tion, Youth and Sports (projects No. MSM 0021620857, RP14/63 and LC06035) and of Grant Agency of Charles University (project SVV 261204) is gratefully acknow- ledged.

REFERENCES

1. Barek J., Fischer J., Navratil T., Peckova K., Yosyp- chuk B., Zima J.: Electroanalysis 19, 2003 (2007). 2. Fed. Reg., EPA Method 604, Phenols, Part VIII, 40

0 2 4 6 8 10 0 1 2 3 4 5 6 I_p (A) t_acc (min)

Fig. 2. Dependence of the peak current of 2-NP and 4-NP on

the accumulation time;  2-NP, unmodified electrode;▲ 2-NP,

MMT-CPE; ● 2-NP, SEP-CPE; □ 4-NP, unmodified electrode;  4-NP, MMT-CPE; ○ 4-NP, SEP-CPE. AdSV, supporting elec- trolyte B-R buffer pH 2, scan rate 20 mV s1_{, pulse amplitude}

50 mV and pulse duration 100 ms

0,8 1,0 1,2 1,4 0,0 0,5 1,0 1,5 2,0 2,5 0,8 1,0 1,2 1,4 0,0 0,5 1,0 1,5 2,0 2,5 3,0 A E (V) B I (A) I (A) E (V)

Fig. 3. Voltammograms of the lowest detectable concentrati-

ons of 2-NP (A) (AdSV, MMT-CPE, concentration 1; 2; 4; 6; 8; 10 and 20 mol L1_{) and 4-NP (B) (DPV, MMT-} CPE, concentration 4; 6; 8; 10 and 20 mol L1_{), dotted line}

corresponding to blank. Supporting electrolyte B-R buffer pH 2, scan rate 20 mV s1, pulse amplitude 50 mV, pulse duration 100 ms

CFR Part 136, Environmental Protection Agency. 3. Agency of toxic substances and disease registry

(http://www.atsdr.cdc.gov/toxprofiles/tp50.html). Accessed 3.3.2010.

4. Wollin K.-M., Dieter H. H.: Arch. Environ. Contam. Toxicol. 49, 18 (2005).

5. Macha S. M., Fitch A.: Mikrochim. Acta 128, 1 (1998).

6. Mousty C.: App. Clay Sci. 27, 159 (2004).

7. Sanchez-Martin M. J., Dorado M. C., del Hoyo C., Rodriguez-Cruz M. S.: J. Hazard. Mater. 150, 115 (2008).

8. Bard A., Mallouk T., in: Techniques of Chemistry: Molecular Design of Electrode Surfaces, (R. W. Murray, ed.) Chap. VI, p. 271. John Wiley, New York 1992.

9. Navrátilová Z., Kula P.: Electroanalysis 15, 837 (2003).

10. El Mhammedi M. A., Achak M., Bakasse M., Chtaini A.: J. Hazard. Mater. 163, 323 (2009).

11. Gomez Y., Fernandez L., Borras C., Mostany J., Scharifker B.: Electroanalysis 21, 1354 (2009). 12. Hu S., Xu C., Wang G., Cui D.: Talanta 54, 115

(2001).

13. Rodriguez I. N., Leyva J. A. M., de Cisneros J. L. H. H.: Anal. Chim., A 344, 167 (1997).

14. Rodriguez I. N., Zamora M. B., Salvador J. M. B., Leyva J. A. M., Hernandez Artiga M. P., de Cisneros J. L. H. H.: Mikrochim. Acta 126, 87 (1997).

15. Švancara I., Metelka R., Vytřas K.: Sensing in Elec- troanalysis, Vol. 1, (K. Vytřas, K. Kalcher, ed.) p. 7, University of Pardubice, Pardubice 2005.

16. Švancara I., Vytřas K.: Anal.Chim.Acta 273, 195 (1993).

Chem. Listy 104, s567s568 (2010) ACP 2010  Súčasný stav a perspektívy analytickej chémie v praxi Posters

USING OF IMPRINTED POLYMERS IN ANALYTICAL CHEMISTRY

NATÁLIA DENDERZ

, JAROSLAV

ŠKUBÁK

, JOZEF ČIŽMÁRIK

,

and JOZEF LEHOTAY

_*

a _{Institute of Analytical Chemistry, Faculty of Chemical}

and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, 812 37 Bratislava, Slovak Re- public, b _{Department of Pharmaceutical Chemistry, Facul-}

ty of Pharmacy, Comenius University, Bratislava, Odbo- járov 10, 832 32 Bratislava, Slovak Republic

[email protected]

Introduction

In present the commonly used methods for sample pretreatment are liquid–liquid extraction (LLE) and solid- phase extraction (SPE). Recently, the attention is paid to molecularly imprinted polymers (MIPs) due to their out- standing advantages, such as predetermined recognition ability, stability, simplicity of preparation, low cost and potential application to a wide range of target molecules1_.

MIPs have been developed in many fields, such as chro- matography, catalyst, drug delivery, artificial antibody, and sensing devices2_{. MIP particles were used as the sta-}

tionary phase of liquid chromatography systems, and the main goal was to improve the separation efficiency, for the enantiomers especially3_.

MIPs are synthetic polymers with highly specific recognition ability for target molecules. In the most com- mon preparation process, monomers form a complex with a template through covalent or non-convalent interactions then they are joined by using a cross-linking agent4_{. By the}

use of the molecular imprinting technique, highly enantio- selective and substrate-selective polymers were prepared by utilizing non-covalent interactions between the tem- plate molecule and methacrylic acid monomers at lower temperature. Previous results showed that imprinted poly- mers could distinguish between enantiomers of the im- printing molecule and even discriminate within a wide range of enantiomers of structurally related molecules that have not been imprinted, but they have the same interac- tion sites with functional monomers5_.

The most widely used technique for preparing MIPs is non-covalent imprinting. In this process, the complex of template and functional monomer is formed in situ by non- covalent interactions, such as hydrogen bonding, electro- static forces, van der Waals forces, or hydrophobic interac- tions. Moreover, the rebinding of template molecules with MIPs is also carried out by the same non-covalent interac- tions. There are several advantages of this technique in- cluding easy preparation of the template/monomer com-

plex, easy removal of the templates from the polymers, fast binding of templates to MIPs, and its potential appli- cation to a wide palette of target molecules. However, to maximize the formation of the labile complex of template and monomer, the conditions of polymerization must be carefully chosen to minimize non-specific binding sites.

Another technique for preparing MIPs is covalent imprinting. The complex is formed by covalent-linkage of a functional monomer and template prior to polymeriza- tion. After the removal of the template by chemical reac- tion, the MIPs contain rebind template molecules via the same covalent interactions. The main advantages of this technique are that the monomer/template complexes are stable and stoichiometric, and that a wide variety of po- lymerization conditions can be employed. Unfortunately, the troublesome and less economical synthesis of mono- mer/template complexes, and the slow release and binding of templates limit its application.

The third technique is the hybridization of covalent and non-covalent imprinting, also called semi-covalent imprinting. In this process, the polymers are prepared like in the same way as in the case of covalent imprinting, but the guest binding employs non-covalent interactions. Thus, semi-covalent imprinting combines the main advantages of the above two techniques6_.