Encapsulation of α-Tocopheryl Acetate into Zeolite Y for Textile

Aug 6, 2010 - Nelson , G. Application of microencapsulation in textiles Int. J. Pharm. ...... Construction of PANI–cellulose composite fibers with g...
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Ind. Eng. Chem. Res. 2010, 49, 8495–8500

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Encapsulation of r-Tocopheryl Acetate into Zeolite Y for Textile Application Eduardo Pe´rez,† Luis Martı´n,‡ Cesar Rubio,† Jose´ S. Urieta,‡ Elena Piera,§ ´ ngel Caballero,§ Carlos Te´llez,*,† and Joaquı´n Coronas† Miguel A Chemical Engineering Department and Nanoscience Institute of Arago´n, UniVersidad de Zaragoza, 50018 Zaragoza, Spain, Organic and Physical Chemistry Department and I3A (Aragon Institute for Engineering Research), UniVersidad de Zaragoza, 50009 Zaragoza, Spain, and Research and DeVelopment Department, Nurel S.A., 50016 Zaragoza, Spain

A useful encapsulation methodology has been developed to fabricate R-tocopheryl acetate-zeolite Y microcapsules. These new microcapsules have been applied to obtain special textile polyamide fibers. The presence of R-tocopheryl acetate in both microcapsules and special fibers has been qualitatively and quantitatively determined using various techniques such as thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), and high performance liquid chromatography (HPLC). Two different techniques to extract the R-tocopheryl acetate encapsulated in both microcapsules and special fibers have been compared: liquid-liquid extraction, that gives the best results under the studied conditions, and supercritical CO2 extraction, which is useful when there are mass transfer limitations as in the case of the special fibers. Mechanical properties of the fiber do not significantly change when they are fabricated with zeolite Y microcapsules. Finally, fabrics knitted with yarns of R-tocopheryl acetate-zeolite Y microcapsules state a significant presence of the additive after 100 washing machine cycles (30 °C, neutral soap). 1. Introduction Today’s textile industry needs innovation and the development of high value-added materials in order to compete. In this context, microencapsulation technology is a growth area in the textile industry.1 Fibers with microcapsules not only behave like conventional fibers but also display different characteristics mainly due to the incorporation of additives in the microcapsules. Textile manufacturers are interested in microcapsules containing fragrances, skin softeners, insect repellents, dyes, vitamins, antimicrobials, phase change materials, antibiotics, hormones, and other drugs.1 Vitamin E (R-tocopherol) is sometimes called the vitamin of life and youth because of its properties in the treatment of certain diseases and its efficacy in fighting the damage that aging and the environment can cause to the skin. This vitamin is considered an excellent ally of beauty and health thanks to its capability of capturing and deactivating free radicals, the oxygen molecules that decompose cellules causing aging. Since vitamin E is unstable under oxidative conditions, it is usually converted into R-tocopheryl acetate which is more stable and more convenient to handle. The microencapsulation process is usually focused on polymeric capsules where additives can be entrapped through several strategies.2 Compared to polymers, inorganic materials generally exhibit much higher stability regarding solvents, pressure, and temperature, and porous materials2-5 are used to prolong the action of the additive. Zeolites have been employed to change polymer properties, for example as an additive to impart antibacterial and flame retardant properties to polymers.6 Zeolite Y is used as an * To whom correspondence should be addressed. Tel.: 34 976 761000 ext. 5429. Fax: 34 976 761879. E-mail: [email protected]. Corresponding author address: University of Zaragoza, c/Marı´a de Luna, 3 50018 Zaragoza, Spain. † Chemical Engineering Department and Nanoscience Institute of Arago´n, Universidad de Zaragoza. ‡ Organic and Physical Chemistry Department and I3A (Aragon Institute for Engineering Research), Universidad de Zaragoza. § Nurel S.A.

encapsulation material for several reasons related to its microporous, adsorption capacity, and crystalline structure.7,8 Zeolite Y has three-dimensional pores with diameters of 0.74 nm, a wide cavity (known as a supercage) with a diameter of 1.2 nm, smaller cavities with internal diameters of 0.5 nm, and, between these smaller cavities, channels with a diameter of 0.22 nm.7 The thermal, mechanical, and chemical stability of the zeolite Y could be transferred to the encapsulated additive; and besides vitamin E can be dosed to ensure a long and regular distribution of its beneficial effect. Like natural zeolites, zeolite Y-based microcapsules are environmentally friendly and are not biologically toxic. Zeolite Y has been used to encapsulate various substances including chromophores and dyes,5,9,10 pheromones,7 ibuprofen,8 semiconductors,11 and catalyst active components.11-13 We have recently developed a useful methodology to encapsulate additives (in this work, R-tocopheryl acetate into zeolite Y) and then use these new microcapsules to obtain special fibers of polyamide 6 which are provided with the beneficial properties of the encapsulated additive.14 Because the microcapsules can withstand the temperatures and other conditions of the industrial manufacturing process, they are added to the process during the spinning of the polyamide 6. This would not be possible with polymeric capsules which are usually applied in the finishing stages15,16 and are therefore attached to the surface of the fibers, limiting their useful life due to use or laundering of the product. In this work, the presence of R-tocopheryl acetate is qualitatively and quantitatively determined in both zeolite Y-based microcapsules and the derived special fibers using different techniques such as thermogravimetric analysis (TGA) and infrared spectroscopy (FTIR) for the microcapsules and high performance liquid chromatography (HPLC) for R-tocopheryl acetate extracted from the microcapsules and special fibers. Furthermore, two different techniques for extracting the R-tocopheryl acetate present in both the zeolite microcapsules and the resulting special fibers are compared. One is a liquid-liquid extraction, where several solvents and extraction conditions

10.1021/ie100483v  2010 American Chemical Society Published on Web 08/06/2010

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Figure 1. Scheme of the preparation of the special fibers additivated with R-tocopheryl acetate. Scanning electron microscopy images done in this figure using a JEOL JSM-6400 operating at 20 kV.

(pressure, temperature, use of condenser, use of autoclave, ...) are tested. The other is an extraction with supercritical CO2, which seeks to exploit the special characteristics of supercritical fluids17 since on one hand they have the penetrability of a gas and on the other the solvent power of a liquid. Other advantages are that their density (related with solute solubility) can be manipulated by varying the pressure and temperature, and, in addition, by means of a fast depressurization, the total separation between solvent and solute may be achieved obtaining a solutefree solvent and a solvent-free solute. Finally, the special fibers were characterized using scanning electron microscopy (SEM), their mechanical properties were measured and compared to fibers without microcapsules, and the influence of washing on the additive permanence in the corresponding fabric was studied. 2. Experimental Procedure 2.1. Zeolite Microcapsules and Special Fibers. The optimized encapsulation process of R-tocopheryl acetate into zeolite Y and the special fibers consists of the following stages (see Figure 1): 1. A pretreatment stage is required to activate the zeolite surface and pores to facilitate the sorption process. Zeolite Y is introduced in a stove at 250 °C for 24 h. 2. In the adsorption or encapsulation stage, the R-tocopheryl acetate and the zeolite Y (3:1, wt/wt) are mixed under vigorous

stirring (IKA-Labortechnik RW 20.n) at 110 °C for 24 h. The separation of the zeolite microcapsules from the obtained suspension is carried out by decantation with distilled water. It is worth noting that the nonencapsulated R-tocopheryl acetate can be recovered and reused after a heating process at 110 °C to remove any existing water. 3. The post-treatment stages consist of the conditioning of the zeolite microcapsules obtained during encapsulation for subsequent industrial application. This includes drying in a stove at 80 °C for approximately 12 h and subsequent grinding and micronization to a particle size of approximately 1-2 µm. 4. The zeolite microcapsules are supplied to the industrial spinning process to obtain the special polyamide-6 fibers. The ratio in weight is 0.37 g of vitamin E-zeolite Y microcapsules to 100 g of special polyamide-6 fibers. More details of the fabrication process of the additivated fibers can be found elsewhere.14 2.2. Extraction. Liquid-Liquid Extraction in Autoclave. This has been used to extract the R-tocopheryl acetate encapsulated in zeolite microcapsules. Several solvents such as ethanol, methanol, and methanol with butylhydroxytoluene (BHT) as antioxidant18 have been tested. Liquid-Liquid Extraction Using a Condenser. This has been used to extract R-tocopheryl acetate encapsulated in zeolite microcapsules and mainly for extraction from the special fibers since the amount of fiber that can be introduced in an autoclave gives rise to diluted solutions below the detection limit. Supercritical CO2 extraction has been used to extract the R-tocopheryl acetate encapsulated into both microcapsules and the resulting special fibers. This has been carried out in a pilot plant, shown in Figure S1 of the Supporting Information. The pressure and temperature conditions of the extractor are 22 MPa and 37 °C, which have been chosen as optimum19 within the range of the plant operation. Two consecutive stages are used, the first without entrainer and the second using ethanol as an entrainer. For more details of typical procedures on liquid-liquid extraction and supercritical CO2 extraction, see the Supporting Information. 2.3. Characterization. For infrared spectroscopy, a FT-IR ATI Mattson Genesis Series spectrometer equipped with a DTGS detector was used. Spectra of the samples were recorded by coadding 32 scans at a resolution of 4 cm-1. Depending on the nature of the samples and to minimize interference in the region of interest, the assays were carried out as follows. Viscous liquid samples, such as standard R-tocopheryl acetate, were impregnated on a NaCl tablet. For powder samples, such as zeolite microcapsules or zeolite Y standards, thin tablets of approximately 50 mg of a mixture of sample and KBr (5:95, wt/wt) were used. Thermogravimetric analysis (TGA) was performed using a TGA/SDTA851e system (Mettler Toledo) in N2 or air flow (20 mL(STP)/min) at a heating rate of 10 °C/min from 25 to 650 °C. The samples were introduced into alumina crucibles of 70 µL. Yarns mechanical properties have been determined with a Zwick 1511 tensile tester. The scanning electron microscopy (SEM) images were collected on a FEI Inspect F50 scanning electronmicroscope operating at 20 kV. For this purpose, slides were prepared embedding fibers in an Epofix cold-setting embedding resin (Electron Microscopy Sciences). Consequently, in volume proportion, 15 parts of embedding resin and 2 parts of hardener were mixed, while the curing time was 8 h at room temperature. The slices were cut at 2 µm thickness approximately using a

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Figure 2. Infrared spectra of vitamin E-zeolite Y microcapsules and standards of R-tocopheryl acetate and zeolite Y.

Leica UC7 with a Standard Ultraknife 45°, 3 mm diamond blade (Drukker Ultramicrotome knife). The different samples were analyzed using a high performance liquid chromatography (HPLC) system consisting of a dual-piston pump (Waters 1515 Isocratic HPLC Pump), a Breeze controller (version 3.20), and a UV-vis detector (Waters 2487 Dual λ Absorbance Detector). A 4.6 × 250 mm 5 µm C18 SunFire column operating at 40 °C was used. The reverse-phase chromatography was carried out with a mobile phase of methanol/water (95:5, v/v) in isocratic mode at a flow rate of 2 mL/min.20,21 The UV detection was set at 295 nm. For the corresponding quantification, the problem samples and the standards were diluted in ethanol and filtered (0.2 µm) as a prior step to analysis. They were then injected with a 25 µL syringe into the equipment in sufficient quantity to fill the loop (5 µL). 2.4. Reagents. All solvents used in the HPLC analysis and in the extractions were HPLC grade quality. Methanol (g99.9%) and butylhydroxytoluene (BHT) were purchased at SigmaAldrich, ethanol (99.5%) at Panreac, liquid CO2 (99.995%) at Abello´ Linde, and ultrapure water was obtained from a Millipore Milli-Q plus ELIX 70 system. The R-tocopheryl acetate (g91.9 wt %) was provided by Cognis (Copherol 1250), whereas the standards of R-tocopherol (g99%), γ-tocopherol (g96%), and δ-tocopherol (∼90%) were supplied by Sigma-Aldrich. The zeolite Y was zeolite Y CBV 100 marketed by Zeolyst with a SiO2/Al2O3 mole ratio of 5.1. 3. Results and Discussion 3.1. Characterization of the Vitamin E-Zeolite Y Microcapsules. The analyses of the different samples by means of infrared spectroscopy have qualitatively revealed the presence of R-tocopheryl acetate in the created zeolite microcapsules. Figure 2 shows the main representative peaks of the R-tocopheryl acetate as well the main peaks corresponding to zeolite Y. As main absorbance peaks22 of the R-tocopheryl acetate, the C-H stretching bands can be observed in the 3000-2840 cm-1 region, the CH3 asymmetric and symmetric stretching (respectively at 1460 and 1375 cm-1) and the CdO stretching and C-O asymmetric stretching corresponding to the phenolic ester at 1760 and 1210 cm-1, respectively. For zeolite Y, the band at 1110-1000 cm-1 is indicative of Si-O stretching.22 Thermogravimetric analyses have been used to quantify the amount of R-tocopheryl acetate present in the vitamin E-zeolite Y microcapsules used in this work. As it can be observed in Figure 3, the weight loss curve of the vitamin E-zeolite Y microcapsules under nitrogen flow shows a first step up to about 225 °C, which corresponds to the weight loss of water (12.2%)

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Figure 3. Thermogravimetric analyses using nitrogen of vitamin E-zeolite Y microcapsules and standards of R-tocopheryl acetate and zeolite Y. Inset: Sample 1 is the vitamin E-zeolite Y microcapsules characterized in this work and used also to produce the fibers. A second sample (sample 2) of vitamin E-zeolite Y microcapsules has been prepared using the same methodology of sample 1 and tested in TGA with nitrogen and air.

in agreement with the water weight loss of pure zeolite Y. There is a second step from 225 °C which corresponds to the loss of encapsulated R-tocopheryl acetate (20.4%). This 20.4% of R-tocopheryl acetate in the zeolite microcapsules would correspond to 0.3025 g of R-tocopheryl acetate/g of dry zeolite Y. In the inset of Figure 3, it can be observed the thermogravimetric analysis of a second sample of the vitamin E-zeolite Y microcapsules prepared with the same procedure as the first sample. For this second sample, the weight loss of encapsulated R-tocopheryl acetate under nitrogen flow is 18.4%, similar to the first sample and indicating the reproducibility of the encapsulation procedure. A thermogravimetric analysis using air of this second sample shows an increase of weight loss of encapsulated R-tocopheryl acetate to 21.4%. That means that a carbonaceous material was produced in the vitamin E using nitrogen, and oxygen causes this material to burn completely. Then in the sample of zeolite microcapsules used to produce the fibers, the quantity of R-tocopheryl acetate can be estimated in 0.3518 g of R-tocopheryl acetate/g of dry zeolite Y. 3.2. Vitamin E Quantification by Using High Performance Liquid Chromatography. By means of this technique it has been possible to quantify the amount of R-tocopheryl acetate extracted from both vitamin E-zeolite Y microcapsules and the resulting special fibers. In the different analyses, apart from the expected R-tocopheryl acetate, other compounds such as R-tocopherol, γ-tocopherol, and δ-tocopherol have been detected. These new compounds would be originated in the hydrolysis25,26 of R-tocopheryl acetate to R-tocopherol and its subsequent demethylation to γ-tocopherol and δ-tocopherol in the extraction process. The hydrolysis would be carried out with the water existing in the zeolite Y and catalyzed by the zeolite itself. To quantify the total amount of extracted R-tocopheryl acetate, the detected amounts of R-, γ-, and δ-tocopherol are added to the obtained amount of R-tocopheryl acetate, even though the combined contribution of these three compounds is practically negligible. A typical chromatogram with the respective peaks of the compounds corresponding to an extraction of vitamin E-zeolite Y microcapsules can be observed in Figure 4. As it has been explained in the experimental procedure, several solvents such as ethanol, methanol, and methanol with BHT have been tested in the different liquid-liquid extractions. The HPLC results of these tests (not shown) show that the amount of extracted R-tocopheryl acetate with the different solvents is comparable. However, slightly better results have been obtained with ethanol.

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Figure 4. Chromatogram of an extraction of vitamin E-zeolite Y microcapsules with ethanol in an autoclave at 130 °C.

Figure 6. Analysis of R-tocopheryl acetate in vitamin E-zeolite Y microcapsules and special fibers by means of HPLC of liquid-liquid extraction using a condenser (with ethanol as solvent at 80 °C) and supercritical CO2 extraction.

Figure 5. Analysis of R-tocopheryl acetate in vitamin E-zeolite Y microcapsules by means of HPLC of liquid-liquid extraction using a condenser (with ethanol as solvent at 80 °C), liquid-liquid extraction in an autoclave (at 90 and 130 °C with ethanol as solvent), and supercritical CO2 extraction.

Figure 5 shows a comparison between the HPLC results obtained with the different extractive techniques carried out on vitamin E-zeolite Y microcapsules. In the liquid-liquid extraction several consecutive extractions have been tested. The supercritical CO2 extraction consists of two consecutive stages, the first without entrainer and the second using ethanol as an entrainer. To compare and note the yield of the different extractive techniques, all the HPLC results shown in Figure 5 have been normalized with regard to the amount of R-tocopheryl acetate existing in the zeolite microcapsules that has been obtained by TGA (the ratio of 0.3518 g of R-tocopheryl acetate/g of dry zeolite Y corresponds to 100% of R-tocopheryl acetate). The R-tocopheryl acetate obtained in the subsequent TGA analysis after the extraction is also added to Figure 5. As it can be observed in Figure 5, the yield of the liquid-liquid extractions increases with the temperature, and the best result is achieved with a liquid-liquid extraction in autoclave at 130 °C. In all the cases, subsequent extraction stages obtain more R-tocopheryl acetate, but the quantity is much lower than in the first stage. For example, at 130 °C, 61.1, 1.9, and 0.5% of the R-tocopheryl acetate is removed from the vitamin E-zeolite Y microcapsules in the first, second and third extraction stage with ethanol. The percentage of total R-tocopheryl acetate obtained adding the extracted R-tocopheryl acetate

and the R-tocopheryl acetate obtained in the subsequent TGA analysis is close to the ratio of 0.3518 g of R-tocopheryl acetate/g of dry zeolite Y (100%). In the first stage of supercritical CO2 extraction without entrainer, the quantity extracted (2.5%) is lower than in the consecutive second stage using ethanol as entrainer (14.2%). This result agrees with other works where ethanol has been used as a cosolvent to increase the amount of extracted natural matter.27 It has been verified that a small amount of ethanol significantly enhances the extraction of polar compounds with supercritical CO2.28 Comparing both kinds of extraction, the yield of the supercritical CO2 extraction is significantly lower than the yield of the liquid-liquid extraction. A similar trend was found by other authors when fatty acids and tocopherols were extracted from peach seed.28 Figure 6 shows the results of the liquid-liquid extraction and supercritical CO2 extraction from special fibers; some results from Figure 5 have been added for comparison. The results have been normalized with regard to the amount of R-tocopheryl acetate present in the vitamin E-zeolite Y microcapsules that has been obtained by TGA and taking into account that the special fibers contain 0.37% (wt) of zeolite microcapsules. The trends in Figure 6 are in agreement with those observed for the vitamin E-zeolite Y microcapsules: the increase in the number of liquid-liquid extraction stages gives rise to an increase in the total R-tocopheryl acetate extracted. In addition, the supercritical CO2 extraction using ethanol as cosolvent is better than without it, and the yield of supercritical CO2 extraction is lower than that of the liquid-liquid extraction. Finally, two points should be noted from Figure 6. a) When liquid-liquid extraction is used, the yield of R-tocopheryl acetate extracted is higher in the vitamin E-zeolite Y microcapsules than in the special fibers. However, when CO2 supercritical extraction is used, the yield of R-tocopheryl acetate extracted is slightly higher for the special fibers than for the vitamin E-zeolite Y microcapsules. b) In the vitamin E-zeolite Y microcapsules the quantity extracted with the supercritical CO2 represents 44% of that achieved with liquid-liquid extraction. With the special fibers, this percentage increases to 61%. These two facts confirm the advantages of supercritical extraction where the mass transfer limitations in the special

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4. Conclusions

Figure 7. Cross section SEM images of a fiber without zeolite (a) and with zeolite Y microcapsules (b). Table 1. Mechanical Properties of Fibers with and without Zeolite Microcapsules

tenacity (cN/Tex) elongation (%) shrinkage (%)

fiber without microcapsules

fiber with microcapsules

38.0 ( 5.0 65.0 ( 6.0 6.0 ( 1.0

32.5 ( 5.0 60.0 ( 6.0 6.0 ( 1.0

fibers could be reduced due to the higher diffusion coefficients in supercritical fluids. Consequently, extraction with supercritical CO2 may be considered a good alternative to conventional liquid-liquid extraction when mass transfer limitations are present. 3.3. Fiber Characterization. Figure 7 shows SEM images of a fiber with zeolite and for comparison a fiber without zeolite. The fiber without zeolite presents TiO2 spherical particles used as white pigment with a size of approximately 200 nm. Besides these TiO2 particles, the fiber with zeolite Y microcapsules presents clearly particles of 1-2 µm. The aspect of these particles correspond to zeolite Y and EDX analysis (not shown) identified the presence of silicon and aluminum. Table 1 shows some mechanical properties of the fibers with and without zeolite microcapsules. Both fibers have 34 filaments and a linear density of 54.0 dtex that means 1000 m fiber weight 5.4 g. The polyamide 6 fiber has a tenacity of 38 centiNewtons/ tex, an elongation at break of 65%, and a shrinkage of 6%. When the zeolite microcapsules are added to the fiber, changes in these properties are minor. There is a slight decrease in the elongation at break when the zeolite microcapsules are incorporated into the polyamide 6 in agreement with the results found when silica has been used as reinforcing filler of nylon 6 resulting in a more brittle23 material. Tenacity, which is a measure of strength of a fiber, decreases slightly and that could be related to the incompatibility between the polymer phase and the filler.24 Finally, shrinkage of the polyamide-6 fibers with zeolite microcapsules was not different from that of polyamide-6 fibers without microcapsules. Anyway, the fiber with and without zeolite can be woven easily. Fabrics knitted with yarns of vitamin E-zeolite Y microcapsules have been subjected to several washing machine cycles (temperature ) 30 °C, neutral soap), and the remaining vitamin E has been determined in the yarn. After 20 washing machine cycles in the yarn remained 60% of the initial vitamin E. After 100 washing cycles the amount of vitamin E was reduced to 27% which demonstrates the permanence of the vitamin E within the fabric. Finally, it should be noted that the zeolite Y microcapsules with R-tocopheryl acetate are the main component to obtain the commercial polyamide-6 yarns called Novarel AntiOX fabric by Nurel S.A.

A useful and simple methodology has been developed and optimized to encapsulate R-tocopheryl acetate into zeolite Y and used to fabricate special fibers additivated with vitamin E. The special fibers are provided with the beneficial properties of the R-tocopheryl acetate, and consequently the skin is also provided with these properties when the final special garments are worn. The introduction of the zeolite microcapsules in the fiber does not affect significantly its tenacity, elongation, and shrinkage. Fabrics knitted with vitamin E-zeolite Y microcapsule yarns state a significant presence of vitamin E even after 100 washing machine cycles. The presence of R-tocopheryl acetate in vitamin E-zeolite Y microcapsules has been qualitatively evaluated by means of infrared spectroscopy. Moreover, the amount of R-tocopheryl acetate encapsulated in these microcapsules has been determined using thermogravimetric analysis. Finally, the R-tocopheryl acetate encapsulated in both microcapsules and the resulting special fibers has been extracted and subsequently quantified by means of high performance liquid chromatography. Different extraction techniques have been used and compared. One is supercritical CO2 extraction where the benefits of ethanol as a cosolvent were demonstrated and another is liquid-liquid extraction where ethanol as a solvent gave the better results. The yield of the liquid-liquid extraction was higher than that of the supercritical CO2 extraction, but CO2 supercritical extraction seems to be a more suitable technique for samples with mass transfer limitations since it increases the diffusivity of the R-tocopheryl acetate. Acknowledgment Financial support from the Spanish Ministry of Science and Innovation (PET2006_0770 and TRA2009_0049) is acknowledged. Supporting Information Available: Extraction of R-tocopheryl acetate and Figure S1. This material is available free of charge via the Internet at http://pubs.acs.org. Literature Cited (1) Nelson, G. Application of microencapsulation in textiles. Int. J. Pharm. 2002, 242, 55. (2) Dong, A.; Wang, Y.; Wang, D.; Yang, W.; Zhang, Y.; Ren, N.; Gao, Z.; Tang, Y. Fabrication of hollow zeolite microcapsules with tailored shapes and functionalized interiors. Microporous Mesoporous Mater. 2003, 64, 69. (3) Yiu, H. H. P.; Wright, P. A.; Botting, N. P. Enzyme immobilisation using siliceous mesoporous molecular sieves. Microporous Mesoporous Mater. 2001, 44-45, 763. (4) Davis, M. E. Ordered porous materials for emerging applications. Nature 2002, 417, 813. (5) Schulz-Ekloff, G.; Wohrle, D.; van Duffel, B.; Schoonheydt, R. A. Chromophores in porous silicas and minerals: preparation and optical properties. Microporous Mesoporous Mater. 2002, 51, 91. ¨ lku¨, S. The effect of (6) Metin, D.; Tihminhoglu, F.; Balkose, D.; U interfacial interactions on the mechanical properties of polypropylene/natural zeolite composites. Composites, Part A 2004, 35, 23. (7) Mun˜oz-Pallares, J.; Corma, A.; Primo, J.; Primo-Yufera, E. Zeolites as pheromone dispensers. J. Agric. Food Chem. 2001, 49, 4801. (8) Horcajada, P.; Marquez-Alvarez, C.; Ramila, A.; Perez-Pariente, J.; Vallet-Regi, M. Controlled release of Ibuprofen from dealuminated faujasites. Solid State Sci. 2006, 8, 1459. (9) Kumar, K. S.; Natarajan, P. Electrochemical behavior of two and one electron redox systems adsorbed on to micro- and mesoporous silicate materials: Influence of the channels and the cationic environment of the host materials. Mater. Chem. Phys. 2009, 117, 365. (10) Pellejero, I.; Urbiztondo, M.; Izquierdo, D.; Irusta, S.; Salinas, I.; Pina, M. P. An optochemical humidity sensor based on immobilized nile red in Y zeolite. Ind. Eng. Chem. Res. 2007, 46, 2335.

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(11) Davis, M. E. Zeolites and molecular sieves: not just ordinary catalysts. Ind. Eng. Chem. Res. 1991, 30, 1675. (12) Hensen, E. J. M.; van Veen, J. A. R. Encapsulation of transition metal sulfides in faujasite zeolite for hydroprocessing applications. Catal. Today 2003, 86, 87. (13) Balkus, K. J.; Khanmamedova, A. K.; Dixon, K. M.; Bedioui, F. Oxidations catalyzed by zeolite ship-in-a-bottle complexes. Appl. Catal., A 1996, 143, 159. (14) Caballero, M. A.; Zagalaz, P.; Segura, S. J.; Piera, M. E.; Pe´rez, E.; Te´llez, C.; Coronas, J.; Santamaria, J. Process for the additivation of synthetic fibres, artificial fibres and polymers with special properties. 2008. Patent numbers: EP1923423-A1, US2008128941-A1, CN101225556-A, KR20080043729-A, TW200837228-A. (15) Rodrigues, S. N.; Fernandes, I.; Martins, I. M.; Mata, V. G.; Barreiro, F.; Rodrigues, A. E. Microencapsulation of limonene for textile application. Ind. Eng. Chem. Res. 2008, 47, 4142. (16) Rodrigues, S. N.; Martins, I. M.; Fernandes, I. P.; Gomes, P. B.; Mata, V. G.; Barreiro, M. F.; Rodrigues, A. E. Scentfashion: Microencapsulated perfumes for textile application. Chem. Eng. J. 2009, 149, 463. (17) Berg, H.; Turner, C.; Dahlberg, L.; Mathiasson, L. Determination of food constituents based on SFE: applications to vitamins A and E in meat and milk. J. Biochem. Biophys. Methods 2000, 43, 391. (18) Huo, J. Z.; Nelis, H. J.; Lavens, P.; Sorgeloos, P.; De Leenheer, A. P. Simultaneous determination of R-tocopheryl acetate and tocopherols in aquatic organisms and fish feed. J. Chromatogr., B 1999, 724, 249. (19) Ge, Y. Q.; Yan, H.; Hui, B. D.; Ni, Y. Y.; Wang, S. X.; Cai, T. Y. Extraction of Natural Vitamin E from Wheat Germ by Supercritical Carbon Dioxide. J. Agric. Food Chem. 2002, 50, 685. (20) Ruperez, F. J.; Mach, M.; Barbas, C. Direct liquid chromatography method for retinol, R- and γ-tocopherols in rat plasma. J. Chromatogr., B 2004, 800, 225.

(21) Ruperez, F. J.; Martin, D.; Herrera, E.; Barbas, C. Chromatographic analysis of R-tocopherol and related compounds in various matrices. J. Chromatogr., A 2001, 935, 45. (22) Pretsch, E.; Bu¨hlmann, P.; Affolter, C. Structure determination of organic compounds. Tables of spectral data, 3rd ed.; Springer-Verlag: 1980. (23) Segatelli, M. G.; Yoshida, I. V. P.; Goncalves, M. D. Natural silica fiber as reinforcing filler of nylon 6. Composites, Part B 2010, 41, 98. (24) Cheng, S.; Shen, D.; Zhu, X.; Tian, X.; Zhou, D.; Fan, L. J. Preparation of nonwoven polyimide/silica hybrid nanofiberous fabrics by combining electrospinning and controlled in situ sol-gel techniques. Eur. Polym. J. 2009, 45, 2767. (25) Kramer-Stickland, K.; Liebler, D. C. Effect of UVB on hydrolysis of alpha-tocopherol acetate to alpha-tocopherol in mouse skin. J. InVest. Dermatol. 1998, 111, 302. (26) Van Henegouwen, G. M. J. B.; Junginger, H. E.; de Vries, H. Hydrolysis of RRR-R-tocopheryl acetate (vitamin E acetate) in the skin and its UV protecting activity (an in vivo study with the rat). J. Photochem. Photobiol., B 1995, 29, 45. (27) Reverchon, E.; De Marco, I. Supercritical fluid extraction and fractionation of natural matter. J. Supercrit. Fluids 2006, 38, 146. (28) Sanchez-Vicente, Y.; Cabanas, A.; Renuncio, J. A. R.; Pando, C. Supercritical fluid extraction of peach (Prunus persica) seed oil using carbon dioxide and ethanol. J. Supercrit. Fluids 2009, 49, 167.

ReceiVed for reView March 4, 2010 ReVised manuscript receiVed June 28, 2010 Accepted July 15, 2010 IE100483V