ИСТИНА

Molecularly imprinted membranes have certain advantages over sorbents obtained by conventional imprinting in bulk, such as shorter polymerization time and easier template removal; they need no grining or sieving of the obtained polymer. Membrane separation is a quasi-one-step process, which does not require a separate analyte desorption stage. Molecularly imprinted membranes have long been applied for separation of various analytes [1], including flavonoids [2]. Membrane preconcentration method has proved efficient. A convenient way of obtaining molecularly imprinted membranes is photopolymerization on polymer supports [3], but it has not been done on track-etched membranes. The feasibility of polymerization within pores of a track-etched membrane was shown in [4]. In this work, photopolymerization was performed on the track-etched membranes (pore size 0.4 m, thickness 10 m, pore density 4•107 cm–2). Methacrylamide (MAA) was used as functional monomer, triethylene glycol dimethacrylate (TEGDMA) as cross-linker, dimethyl¬formamide as porogenic solvent, Darocur 1173 (2-hydroxy-2-methyl¬-1-phenyl-propan¬1-one) as phootinitiator. To obtain an imprinted membrane, rutin or naringenin (0.1 % w.) as templates were also added to the mixture. The track-etched membrane was wetted with the polyme¬rization mixture, pressed between two glass slides and irradiated with UV light during up to 60 min. After polymerization, the template was washed out by acetone under control by UV-vis spectrum. The diffusional properties of the obtained membranes were carried out on a plastic Millipore filter holder with additionally drilled openings. Deaeration of the system was unnecessary if the polymerization was carried out between the glass slides, which apparently restricted the access of oxygen into the polymerizing mixture. If the membrane was irradiated in open air, only modification of the membrane pore walls was observed; however, the imprints of naringenin could be obtained, as can be judged by membrane diffusional permeability. The diffusion rates of the obtained imprinted membranes were higher than those for initial unmodified track-etched membrane. This is consistent with earlier observations for membranes physically modified with Nafion [5]. Almost equilibrium amount of the flavonoid was transported from the feed to the permeate in 10 min. Ascorbic acid transport across imprinted membranes is suppressed. Selectivity factor SF(A/B) was calculated as the ratio of diffusion rates of the analyte A and component B. For rutin-imprinted membrane, SF(rutin/naringenin) = 17, and for naringenin¬imprinted membrane SF(naringenin/quercetin) = 9. This implies that selective membrane separation of a single flavonoid may be feasible, provided more data on the permeability of other flavonoids are collected. References [1] M. Ulbricht, Membrane separations using molecularly imprinted polymers. J. Chrom. B, 804, 113–125 (2004). [2] F. Trotta, E. Drioli, C. Baggiani, D. Lacopo, Molecular imprinted polymeric membrane for naringin recognition. J. Membr. Sci, 201, 77–84 (2002). [3] X.J. Qu, Q.X. Meng, S.Y. Ai, J. Zhou, L.S. Zhu, Recognition of 6-benzyladenine using a molecularly imprinted membrane on a cellulose acetate support. J. Analyt. Chem., 63, 999–1004 (2008). [4] A. Kros, R.J.M. Nolte, N.A.J.M. Sommerdijk, Adv. Mater., 14, 1779–1782 (2002). Authors thank the Russian Foundation for Basic Research (project No 10-03-01023a) for financial support and Ciba Special Chemical Service Inc. for donating Darocur 1173.