Enantioselective sorption of some chiral carboxylic acids by various cyclodextrin-grafted iron oxide magnetic nanoparticles

Tetrahedron: Asymmetry 24 (2013) 982–989

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Enantioselective sorption of some chiral carboxylic acids by various cyclodextrin-grafted iron oxide magnetic nanoparticles Mustafa Arslan a,b, Serkan Sayin a, Mustafa Yilmaz a,⇑ a b

Department of Chemistry, Selcuk University, Konya 42075, Turkey Department of Chemistry, Kirklareli University, Kirklareli 39000, Turkey

a r t i c l e

i n f o

Article history: Received 16 May 2013 Accepted 16 July 2013

a b s t r a c t A new enantioselective sorption approach to chiral carboxylic acid molecules such as (R)-()-N-(3,5-dinitrobenzoyl)phenylglycine (R)-()DNBPG, (S)-(+)-N-(3,5-dinitrobenzoyl)phenylglycine (S)-(+)DNBPG, (R)-(+)-N-(1-phenylethyl)phthalamic acid (R)-(+)PEPA and (S)-()-N-(1-phenylethyl)phthalamic acid (S)-()PEPA regarding their complexation with three diversely functionalized b-cyclodextrin grafted iron oxide nanoparticles in the aqueous phase, was developed. The sorption efficiencies of these carboxylic acids were carried out by high-performance liquid chromatography (HPLC) with an Ace 5 C18 column. The effects of temperatures on the sorption were also investigated. The results showed that the ether functionalized derivative of b-cyclodextrin Al-CD-MNPs has a specific affinity for (R)-()DNBPG at 30 °C and pH 7.0. The amine functionalized derivative of b-cyclodextrin Am-CD-MNPs has a greater affinity towards not only (S)-()DNBPG, but also (R)-(+)PEPA compared with their other isomers, which are the (R)-isomer of DNBPG and the (S)-isomer of PEPA at 30 °C and pH 7.0. In addition, although amide functionalized derivatives of b-cyclodextrin (Amd-CD-MNPs) have an affinity towards both isomers of some chiral carboxylic acids; no selective affinity was observed at 30 °C and pH 7.0. Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction Proteins and polysaccharides comprised from amino acids and carbohydrates have chiral structures, and their unique enantiomeric forms can be found in Nature.1 It is well-known that enantiomers hold a special position for selective molecular interactions, which are of essential importance in biochemical processes such as molecular transport, protein assembly and genetic information processing.2 Pure enantiomers of carboxylic acids are essential building blocks of natural products and other important biomolecules, chiral drugs and catalysts.3,4 In recent years, magnetic nanoparticles and their composites have become crucial in nanotechnology, catalysis, sensing devices, cell labelling and separations, bio-imaging, targeted drug delivery and biomedical applications.5–10 As a result, the immobilization of some molecules such as macrocyclic host molecules onto magnetic nanoparticles has attracted considerable attention due to the unique size and physical properties of nano-materials when compared to their bulk materials.5 Cyclodextrins (CDs) obtained by enzymatic degradation of starch, are a well-known class of supramolecules.11 Having primary and secondary hydroxyl groups, and a cyclic structure ⇑ Corresponding author. Tel.: +90 332 2232774; fax: +90 332 2410106. E-mail address: [email protected] (M. Yilmaz). 0957-4166/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tetasy.2013.07.015

makes them indispensable.11 Moreover, the surrounding walls of cyclodextrin-bearing hydroxyl groups, provide water solubility, whereas the central cavity of the cyclodextrins is hydrophobic.12 The complex formation and chiral recognition ability of CDs allow widespread application in chemistry, pharmaceuticals, foods, agrochemicals, enzyme mimics, enantioselective catalysts, drug carriers, odors and taste-masking compounds.13 Host–guest type complexation of cyclodextrins has recently received much attention for their contribution in understanding non-covalent interactions in their cavity and their applications in many fields.2,14 Herein, three different b-cyclodextrins with a linker based on an amide, ether or amine were synthesized and grafted onto the surface of iron oxide nanoparticles in order to investigate their sorption capabilities towards some chiral carboxylic acids (see Fig. 1) such as (R)-()-N-(3,5-dinitrobenzoyl)phenylglycine, (S)-(+)-N-(3,5-dinitrobenzoyl)phenylglycine, (R)-(+)-N-(1-phenylethyl)phthalamic acid and (S)-()-N-(1-phenylethyl)phthalamic acid at different pH values and temperatures. The magnetic properties of these b-cyclodextrin nanoparticles easily provide separation with respect to reducing the effort required for such separations. 2. Results and discussion Herein we have focused on the synthesis and preparation of b-cyclodextrin-grafted magnetic nanoparticles with different

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NO2

NO2

O

O H N

O2N

H N OH

O2N

OH O

O

(R)-(-)-N-(3,5-dinitrobenzoyl)phenylglycine

O

(S)-(+)-N-(3,5-dinitrobenzoyl)phenylglycine

O OH H N

O

OH H N CH3

(R)-2-(1-phenylethylcarbamoyl)benzoic acid

O

CH3

(S)-2-(1-phenylethylcarbamoyl)benzoic acid

Figure 1. Molecular structures of the carboxylic acids.

linkers depending on the amine, ether or amide, as well as their usage in the enantioselective separation of some chiral carboxylic acids such as (R)-()-N-(3,5-dinitrobenzoyl)phenylglycine, (S)-(+)N-(3,5-dinitrobenzoyl)phenylglycine, (S)-()-N-(1-phenylethyl)phthalamic acid and (R)-(+)-N-(1-phenylethyl)phthalamic. All of the novel molecules were characterized by NMR, FTIR, TGA, TEM, VSM and elemental analysis. However, in order to achieve our desired goal, b-cyclodextrin was initially treated with p-toluenesulfonyl chloride to afford mono-tosylated b-cyclodextrin 1 according to the literature.15,16 Compound 1 was then selectively interacted with (3-aminopropyl)triethoxysilane to produce monoaminosilica-functionalized b-cyclodextrin 2 (Am-CD). The disappearance of the tosyl group and the appearance of new peaks at 0.48 and 2.80 ppm deriving from (3-aminopropyl)triethoxysilaneb-cyclodextrin in the 1H NMR spectrum confirmed the structure of Am-CD 2. The 13C NMR has also proved the structure of Am-CD (see Fig. 2). The reaction of b-cyclodextrin with [3-(2,3-epoxypropoxy)propyl]trimethoxysilane or 3-(trietoxysilyl)propyl isocyanate under convenient reaction conditions gave the alcohol silica-functionalized b-cyclodextrin 3 (Al-CD)17 or amide silica-functionalized b-cyclodextrin 4 (Amd-CD) meaning that a convenient binding side was provided for their immobilization onto iron oxide nanoparticles (see Scheme 1). The 1H NMR spectrum of Al-CD 3 confirmed that the desired compound 3 was produced by the appearance of additional peaks at 2.70, 2.86, 3.34 and 3.70 ppm, which belong to diethoxy(3-glycidyloxypropyl)methylsilane. The 1 H NMR spectrum shows that Amd-CD 4 has a characteristic peak at 7.95 ppm, which comes from an amide proton. The 13C NMR also confirmed the structures of Al-CD and Amd-CD (see Fig. 2). Subsequently, three different silica-based b-cyclodextrins 2,3,4 were grafted onto iron oxide magnetic nanoparticles to obtain Am-CD-MNPs, Al-CD-MNPs and Amd-CD-MNPs, respectively. The formation of Am-CD-MNPs, Al-CD-MNPs and Amd-CD-MNPs was confirmed by a combination of FTIR, TEM, TGA, VSM and elemental analysis. FTIR spectroscopy was used for elaborating upon the structure of Fe3O4, Am-CD-MNPs, Al-CD-MNPs and Amd-CD-MNPs. The FTIR spectra showed that the immobilization of Am-CD, Al-CD and Amd-CD onto iron oxide magnetic nanoparticles has been achieved (see Figs. 3–5). The transmission electron microscopy (TEM) micrographs of pure Fe3O4 nanoparticles, Am-CD-MNPs, Al-CD-MNPs and Amd-

CD-MNPs were evaluated to gain more information on the particle size and morphology (see Fig. 6a–d). The particle sizes of pure Fe3O4 nanoparticles, Am-CD-MNPs, Al-CD-MNPs and Amd-CDMNPs were found to be about 4 ± 2 nm for pure Fe3O4 (Fig. 6a), 7–11 nm for Am-CD-MNPs, Al-CD-MNPs and Amd-CD-MNPs (Fig. 6b–d), respectively. The grafted units of CD derivatives, which have many hydrophilic units that are able to cause aggregation, resulted with increasing particle size of MNPs after immobilization of diversely functionalized silica-based cyclodextrins. Thermogravimetric analysis (TGA) was used to determine the amount of CDs (Al-CD, Am-CD and Amd-CD) onto the surface of the magnetic nanoparticles. As shown in Figure 7a–c, the TGA curves of CD-MNPs showed that the weight loss of 33%, 40% and 20% mass was due to the decomposition of CD and the silica parts of the Am-CD, Al-CD and Amd-CD in the range of 200–550 °C, respectively. In order to estimate the magnetic behaviours of pure Fe3O4, AlCD-MNPs and Am-CD-MNPs, a vibrating sample magnetometer (VSM; Lake Shore 7407) was used at room temperature in order to capture the hysteresis loops of the CD-MNPs (see Fig. 8). The saturation magnetizations of Am-CD-MNPs and Al-CD-MNPs were observed to be 31 and 22 emu/g, whereas the saturation magnetization of pure Fe3O4 was 44 emu/g. This difference illustrates the fact that the binding of the CD influenced the magnetic behaviour of the Fe3O4 cores by decreasing it with regard to unmagnetizing the CDs surrounding the nanoparticle surface. This resulted in a lowered magnetization value. Table 1 shows the elemental analysis results of Am-CD-MNPs and Amd-CD-MNPs evolving into nitrogen since Am-CD and Amd-CD provided nitrogen onto the iron oxide nanoparticle via immobilization. As can be seen in Table 1, Am-CD-MNPs and Amd-CD-MNPs contain 0.56% and 0.94% nitrogen corresponding to 0.40 and 4.72 mmol of Am-CD-MNPs and Amd-CD-MNPs/g of support, respectively. 3. Sorption studies Enantiomeric separation of chiral molecules is regarded as a hot topic in chemistry. For this reason many researchers are focusing on this field.18,19 In this sense, supramolecular aspects associated with host–guest and self-assembly interactions have recently been employed for enantioselective studies.20,21 Cyclodextrins are one of the supramolecular compounds being used for enantioselective

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differently functionalized CD-grafted magnetic nanoparticles were performed and assessed by HPLC. WE also looked at the influence of varying the temperature (Figs. 9 and 10). It was observed that all of CD-grafted magnetic nanoparticles had an affinity towards carboxylic acids with different percentages at both 30 and 50 °C. Hence, Am-CD-MNPs stood out with a remarkable selective sorption. As can be seen in Figures 9 and 10, the (S)-(+)-N-(3,5-dinitrobenzoyl)phenylglycine enantiomer was absorbed with 46% (at 30 °C) and 53% (at 50 °C) at pH 7.0 by the Am-CD-MNPs, whereas the (R)-()-N-(3,5-dinitrobenzoyl)phenylglycine enantiomer was not carried. Similarly, the (S)-()-N-(1-phenylethyl)phthalamic acid enantiomer was absorbed with a percentage of 29% (at 30 °C) and 31% (at 50 °C) at pH 7.0 by the Am-CD-MNPs, while the (R)-(+)-N-(1-phenylethyl)phthalamic acid enantiomer was not carried. These findings clarify that three differently functionalized CD-grafted iron oxide magnetic nanoparticles have sorption affinity towards some carboxylic acids. The sorption mechanism might proceed by forming significant hydrogen bonding and host–guest interaction between the carboxylic acids and CD-grafted magnetic nanoparticles (Al-CD-MNPs, Am-CD-MNPs and Amd-CD-MNPs). 4. Conclusion Three new cyclodextrin derivatives were synthesized and grafted onto iron oxide nanoparticles in order to prevent the unwanted water solubility of the CD and provide an easy method for the separation of molecules after their applications. Moreover, the immobilization of CDs onto iron oxide magnetic nanoparticles provides a surface diversity associated with enhancing the stability of the CD. The three novel CD-grafted magnetic nanoparticles were examined for their enantioselective separation capabilities towards some chiral carboxylic acids such as (R)-()-N-(3,5-dinitrobenzoyl)phenylglycine, (S)-(+)-N-(3,5-dinitrobenzoyl)phenylglycine, (S)-()-N-(1-phenylethyl)phthalamic acid and (R)-(+)-N-(1-phenylethyl)phthalamic acid). In addition, the effects of pH and temperature were also evaluated. It was found that all of the CD-MNPs had an affinity towards these carboxylic acids. Al-CD-MNPs exhibited more selectivity for (R)-()DNBPG than the (S)-enantiomer of DNBPG at 30 °C and pH 7.0. Am-CD-MNPs had a great capability towards (S)-()DNBPG as well as (R)-(+)PEPA but no selectivity towards the (R)-isomer of DNBPG and the (S)-isomer of PEPA at 30 °C and pH 7.0. However, selective separation was observed for Am-CD-MNPs at 30 and 50 °C. It was concluded that the complexation of carboxylic acid molecules depends on the structural properties of the cyclodextrin-immobilized iron oxide nanoparticles such as hydrophobic cavity size, stability or rigidity and hydrogen binding ability. It also depends upon the electrostatic interactions or ion-dipole attractions between the CD-MNPs and the acid molecules.

5. Experimental Figure 2.

13

C NMR spectrum of (a) Am-CD, (b) Amd-CD, (c) Al-CD.

studies. However, three cyclodextrin derivatives have been synthesized and grafted onto iron oxide magnetic nanoparticles in order to prevent their water solubility as well as create easy separation capability for them after application in the enantioselective separation of some chiral carboxylic acids by using a sorption system. Enantioselective studies of some carboxylic acids such as (R)-()N-(3,5-dinitrobenzoyl)phenylglycine, (S)-(+)-N-(3,5-dinitrobenzoyl)phenylglycine, (S)-()-N-(1-phenylethyl)phthalamic acid and (R)-(+)-N-(1-phenylethyl)phthalamic acid in the presence of three

5.1. Reagents b-Cyclodextrin (CD) was purchased from Fluka and used directly. (R)-()-N-(3,5-dinitrobenzoyl)phenylglycine, (S)-(+)-N(3,5-dinitrobenzoyl)phenylglycine, (S)-()-N-(1-phenylethyl)phthalamic acid and (R)-(+)-N-(1-phenylethyl)phthalamic acid were purchased from Sigma (St. Lois, MO, USA) and used without further purification. Epoxypropxypropyltrimethoxysilan, aminopropyltriethoxysilan and isocyanatopropyltriethoxysilane, and all solvents were bought from Aldrich and Merck. Analytical Thin Layer Chromatography (TLC) was performed using Merck plates (silica gel 60 F254 on aluminium). All aqueous solutions were

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Scheme 1. Preparation of Am-CD-MNPs, Al-CD-MNPs and Amd-CD-MNPs. Reaction conditions: (i) (3-aminopropyl)triethoxysilane, triethylamine, 60 °C, 46 h; (ii) [3-(2,3-epoxypropoxy)propyl]trimethoxysilane, DMF, 50 °C, 3 h; (iii) 3-(triethoxysilyl)propyl isocyanate, DMF, 70 °C, 6 h; (iv) FeCl24H2O, Fe(NO3)39H2O, SDS, TEOS, NH3, xylene, 80 °C, N2 atmosphere.

Figure 3. FTIR spectra of Am-CD-MNPs.

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Figure 4. FTIR spectra of Al-CD-MNPs.

Figure 5. FTIR spectra of Amd-CD-MNPs.

prepared with deionized water that had been passed through a Millipore milli-Q Plus water purification system. 5.2. Apparatus NMR spectra were recorded on a Varian 400 MHz spectrometer. FTIR spectra were evaluated on Perkin Elmer spectrum 100 FTIR spectrometer. Shimadzu 160A UV–visible recording spectrophotometer was used for UV–vis. spectra. Thermogravimetric analysis (TGA) was carried out with Seteram Evalution-1750 thermogravimetric analyser and performed under an argon atmosphere. Transmission electron microscopy (TEM) analysis was carried out with FEI Tecnai G2 Spirit. Melting points were determined on a EZ-Melt apparatus in a sealed capillary. An Orion 410A+ pH meter was used for the pH measurements. 5.3. Synthesis Mono-6-deoxy-6-tosyl-b-cyclodextrin 1, alcohol silicafunctionalized b-cyclodextrin 3 and Al-CD-MNPs were synthesized

according to the literature.15–17 The syntheses of amino silicafunctionalized b-cyclodextrin 2 and amide silica-functionalized b-cyclodextrin 4, and their immobilization onto iron oxide nanoparticles have been reported for the first time. 5.3.1. Synthesis of mono-6-deoxy-6-tosyl-b-cyclodextrin (Ts-bCD) 1 Yield 83%, 1H NMR (400 MHz, DMSO): d (ppm) 2.43 (s, 3H, – CH3), 3.35–3.15 (m, HOD shielded, 12H), 3.80–3.41 (m, 30H), 4.60–4.41 (m, 6H, OH), 4.91–4.75 (m, 7H), 5.85–5.65 (m, 14H, OH), 7.48 (d, 2H, J = 8.21 Hz, ArH), 7.79 ppm (d, 2H, J = 8.21 Hz, ArH). 5.3.2. Synthesis of amine functionalized b-cyclodextrin (Am-CD) 2 To a solution of mono-6-deoxy-6-tosyl-b-cyclodextrin 1.0 g (0.7 mmol) in 6 mL of triethylamine was added 30 mL of (3-aminopropyl)triethoxysilane at 60 °C, and allowed to stir for 46 h. Next, acetone was poured into the mixture to form a precipitate. The collected product was dried at 60 °C in a vacuum oven. Yield 40%; 1H

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987

Figure 6. TEM micrographs of (a) pure Fe3O4 nanoparticles, (b) Al-CD-MNPs, (c) Amd-CD-MNPs, (d) Am-CD-MNPs.

NMR (400 MHz, DMSO): d (ppm) 0.48 (br, 9H), 1.05 (br, 2H), 1.58 (br, 2H, CH2NH), 2.80 (br, 2H, SiCH2), 3.55–3.44 (m, 20H), 3.76– 3.69 (m, 22H), 3.88–3.79 (m, 6H), 4.60 (br, 6H, OH), 4.49 br, 7H). 13 C NMR (400 MHz, DMSO): d (ppm) 17.41, 31.15, 60.36, 72.49, 72.87, 73.49, 81.99, 102.39. Anal. Calcd for C105H217N7O49Si7: C, 49.29; H, 8.55; N, 3.83. Found: C, 49.17; H, 8.68; N, 3.74. 5.3.3. Synthesis of alcohol functionalized b-cyclodextrin (Al-CD) 3 Yield 71.8%, 1H NMR (400 MHz, DMSO): d (ppm) 2.70 (br, 14H), 2.86 (br, 14H), 3.34–3.26 (m, 42H), 3.70–3.42 (m, 119H), 4.81 (d, 21H, J = 5.48 Hz). 13C NMR (400 MHz, DMSO): d (ppm) 31.23, 36.24, 60.39, 72.50, 72.89, 73.52, 81.99, 102.40. Anal. Calcd for C126H252O70Si7: C, 49.07; H, 8.24. Found: C, 49.18; H, 8.08. 5.3.4. Synthesis of amide functionalized b-cyclodextrin (AmdCD) 4 3-(Triethoxysilyl)propyl isocyanate (4.36 mL, 26 mmol) was added dropwise to a solution of b-cyclodextrin (2 g, 1.762 mmol) in 10 mL of dry DMF at 70 °C. The mixture was stirred for 6 h and precipitated by the addition of acetone. The collected solid was dried in a vacuum oven at 60 °C. Yield 72.5%; FT-IR (cm1): 1716 (C@O), 1654 (NC@O); 1H NMR (400 MHz, DMSO): d (ppm) 0.5 (br, 7H), 1.1–1.2 (m, 14H), 1.4 (br, 7H), 3.2–3.5 (m, 42H), 3.6– 3.7 (m, 63H), 3.7–3.8 (m, 14H), 4.8 (br, 7H), 5.7–5.8 (m, 14H), 7.9 (s, 7H). 13C NMR (400 MHz, DMSO): d (ppm) 18.9, 31.5, 36.5, 58.4, 60.6, 72.7, 73.1, 73.7, 82.2, 102.8, 163.0. Anal. Calcd for C112H217N7O63Si7: C, 46.93; H, 7.63; N, 3.42. Found: C, 47.01; H, 7.56; N, 3.34.

5.3.5. General procedure for the preparation of Am-CD-MNPs, Al-CD-MNPs and Amd-CD-MNPs At first, FeCl24H2O (1 g, 5 mmol) and Fe(NO3)39H2O (4.1 g, 10 mmol) were dissolved in 9 mL of deionized water under an N2 atmosphere for 10 min at 80 °C, and a solution of sodium dodecyl sulfate (1.5 g, 5 mmol) in 20 mL of xylene was added over 15 min, and then purged with N2 for 15 min. When 10 mL of NH3 was added to this mixture, the formation of particles with color change occurred. After stirring the mixture at 80 °C for 3 h, the temperature of the reaction was lowered to room temperature. Next, 10 mL of TEOS and 2.5 g (2 mmol) of b-cyclodextrin derivative Am-CD, Al-CD or Amd-CD were added to that mixture and stirred further 14 h at rt. Ethanol was added to the mixture to afford CD-grafted magnetic nanoparticles Am-CD-MNPs, Al-CDMNPs or Amd-CD-MNPs and collected by using a magnet, washed with ethanol and water and dried in a vacuum oven at 60 °C. 5.4. Solid–liquid sorption The sorption properties of the generated CD-grafted magnetic nanoparticles Am-CD-MNPs, Al-CD-MNPs and Amd-CD-MNPs were assessed by the following technique.22 Into a stoppered flask, a sorbent (25 mg) and 10 mL (2  105 M) of an aqueous solution of carboxylic acid derivatives ((R)-()-N-(3,5-dinitrobenzoyl)phenylglycine, (S)-(+)-N-(3,5-dinitrobenzoyl)phenylglycine, (S)-()-N(1-phenylethyl)phthalamic acid and (R)-(+)-N-(1-phenylethyl)phthalamic acid) were added at 25 °C, which was then shaken on a mechanical shaker operating at a constant agitation speed of 170 rpm for 1 h. The sorbent was separated before

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Figure 8. Magnetization versus applied magnetic field for pure Fe3O4 nanoparticles, Am-CD-MNPs and Al-CD-MNPs at 300 K.

Table 1 Results of the elemental analysis for Am-CD-MNPs and Amd-CD-MNPs

Am-CD-MNPs Amd-CD-MNPs a

C (%)

H (%)

N (%)

Bonded amounta (mmol/g)

25.12 10.65

4.096 2.471

0.562 0.943

0.401 4.72

Calculated according to the N content.

Figure 9. The percent sorption (S%) of compounds Am-CD-MNPs, Al-CD-MNPs and Amd-CD-MNPs for (R)-()-N-(3,5-dinitrobenzoyl)phenylglycine (R)-()DNBPG, (S)-()-N-(3,5-dinitrobenzoyl)phenylglycine (S)-()DNBPG, (R)-(+)-N-(1-phenylethyl)phthalamic acid (R)-(+)PEPA and (S)-(+)-N-(1-phenylethyl)phthalamic acid (S)-(+)PEPA at 30 °C and pH 7.0. Mobile phase: methanol (A) and water (B), Flow rate: 1 ml/dk, 25 °C, injection volume: 20 lL, 254 nm in the HPLC.

Figure 7. TGA curves of (a) Am-CD-MNPs, (b) Al-CD-MNPs, (c) Amd-CD-MNPs.

measurements by using a simple magnet. The residue concentration of the solute was analysed by HPLC analyses recorded at kmax for each solution at 254 nm. Moreover, two different temperatures (30 and 50 °C) were studied in order to determine the effect of the temperature on the sorption. The experiments were performed in triplicate.

Figure 10. The percent sorption (S%) of compounds Am-CD-MNPs, Al-CD-MNPs and Amd-CD-MNPs for (R)-()-N-(3,5-dinitrobenzoyl)phenylglycine (R)()DNBPG, (S)-()-N-(3,5-dinitrobenzoyl)phenylglycine (S)-()DNBPG, (R)-(+)-N(1-phenylethyl)phthalamic acid ((R)-(+)PEPA) and (S)-(+)-N-(1-phenylethyl) phthalamic acid (S)-(+)PEPA at 50 °C and pH 7.0. Mobile phase: methanol (A) and water (B), Flow rate: 1 ml/dk, 25 °C, injection volume: 20 lL, 254 nm in the HPLC.

The percent sorption (S%) was calculated according to Eq. (1):

ðS%Þ ¼

A0  A  100 A0

ð1Þ

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where A0 and A are the initial and final concentrations of the carboxylic acids before and after the extraction, respectively. Acknowledgments We would like to thank The Research Foundation of Selcuk University (BAP) for financial support of this work. This study is a part of M.Sc Thesis of Mustafa Arslan. References 1. Sancho, R.; Minguillo, C. Chem. Soc. Rev. 2009, 38, 797–805. 2. Iuliano, A.; Attolino, E.; Salvadori, P. Tetrahedron: Asymmetry 2002, 13, 1805– 1815. 3. Zheng, Y. S.; Hu, Y. J.; Li, D. M.; Chen, Y. C. Talanta 2010, 80, 1470–1474. 4. Luo, Z.; Zhong, C.; Wu, X.; Fu, E. Tetrahedron Lett. 2008, 49, 3385–3390. 5. Luo, X.; Morrin, A.; Killard, A. J.; Smyth, M. R. Electroanalytical 2006, 18, 319– 326. 6. Corti, M.; Lascialfari, A.; Micotti, E.; Castellano, A.; Donativi, M.; Quarta, A.; Cozzoli, P. D.; Manna, L.; Pellegrino, T.; Sangregorio, C. J. Magn. Magn. Mater. 2008, 320, E320–E323.

989

7. Jun, Y. W.; Huh, Y. M.; Choi, J. S.; Song, H. T.; Kim, S.; Yoon, S.; Kim, K. S.; Shin, J. S.; Suh, J. S.; Cheon, J. J. Am. Chem. Soc. 2005, 127, 5732–5733. 8. Song, H. T.; Choi, J. S.; Huh, Y. M.; Kim, S.; Jun, Y. W.; Suh, J. S.; Cheon, J. J. Am. Chem. Soc. 2005, 127, 9992–9993. 9. Liu, T. Y.; Hu, S. H.; Liu, K. H.; Liu, D. M.; Chen, S. Y. J. Controlled Release 2008, 126, 228–236. 10. Chen, F. H.; Gao, Q.; Ni, J. Z. Nanotechnology 2008, 19, 165103. 11. Szente, L.; Fenyvesi, E.; Szejtli, J. Environ. Sci. Technol. 1999, 33, 4495–4498. 12. Lucas-Abellán, C.; Fortea, I.; Antonio, J.; Gabaldón, J. A.; Núñez-Delicado, E. J. Agric. Food Chem. 2008, 56, 255–259. 13. Bezhan, C. Chem. Soc. Rev. 2004, 33, 337–347. 14. Hartman, T.; Herzig, V.; Budšínsky, M.; Jindrˇich, J.; Cibulka, R.; Kraus, T. Tetrahedron: Asymmetry 2012, 23, 1571–1583. 15. Namazi, H.; Kanani, A. J. Bioact. Compat. Polym. 2007, 22, 77. 16. Zhong, N.; Byun, H. S.; Bittman, R. Tetrahedron Lett. 1998, 39, 2919–2920. 17. Arslan, M.; Sayin, S.; Yilmaz, M. Water, Air, Soil Pollut. 2013, 224, 1527. 18. Hinze, W. L.; Riehl, T. E.; Armstrong, D. W.; DeMond, W.; Alak, A.; Ward, T. Anal. Chem. 1985, 57, 237–242. 19. Hilton, M.; Armstrong, D. W. J. Liq. Chromatogr. Related Technol. 1991, 14, 3673– 3683. 20. Sayin, S.; Yilmaz, E.; Yilmaz, M. Org. Biomol. Chem. 2011, 9, 4021–4024. 21. Ozyilmaz, E.; Sayin, S. Bioprocess Biosyst. Eng. 2013, in press. 22. Yilmaz, E.; Memon, S.; Yilmaz, M. J. Hazard. Mater. 2010, 174, 592–597.