Comparison of ordered mesoporous materials sorption properties towards amino acids
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Comparison of ordered mesoporous materials sorption properties towards amino acids Joanna Goscianska • Anna Olejnik Robert Pietrzak
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Received: 28 November 2012 / Accepted: 18 January 2013 / Published online: 2 February 2013 Ó The Author(s) 2013. This article is published with open access at Springerlink.com
Abstract The adsorption of amino acids such as L-phenylalanine and L-histidine was carried out on a series of mesoporous carbons obtained with the use ordered silicas KIT-6, SBA-16, SBA-15 as templates and furfuryl alcohol as carbon precursor. Small angle XRD analysis confirmed the ordered mesoporous structures of all materials obtained. They were also characterised by well-developed surface areas and high pore volumes. Adsorption behaviour of amino acids on ordered mesoporous carbons was investigated in potassium phosphate buffer solutions with adjustable L-phenylalanine and L-histidine concentration, ion strength, and pH. The highest sorption capacity towards the amino acids were observed at pH close to the isoelectric point of L-phenylalanine (pI = 5.48) and L-histidine (pI = 7.59). Electrostatic, hydrophobic and steric interactions had very strong effect on the adsorption of amino acids on mesoporous carbons. The amount of L-phenylalanine and L-histidine adsorbed decreased in the following sequence: CKIT-6 [ CSBA-16 [ CSBA-15 that was strongly related to their structure, surface areas and average pore diameters. Keywords Adsorption of L-phenylalanine L-histidine Amino acids Mesoporous carbons Furfuryl alcohol
1 Introduction Amino acids, the components of protein, play an important role in many fields, including food industry and solid-phase peptide synthesis (Meng et al. 2004). They are also applied J. Goscianska A. Olejnik R. Pietrzak (&) Faculty of Chemistry, Adam Mickiewicz University in Poznan´, Umultowska 89b, 61-614 Poznan´, Poland e-mail: [email protected]
as building blocks for the production of pharmaceutical and agrochemical compounds (O’Connor et al. 2006). In order to make amino acids useful in the above mentioned fields, they should be placed on the surface of solid materials (Vinu et al. 2006), therefore they should be adsorbed. Additionally, the investigation on the adsorption of amino acids can provide important information on separation and purification of these biomolecules (Munsch et al. 2001). Furthermore, the molecular size and zwitterionic nature make amino acids an attractive adsorbate model. So far the adsorption of amino acids has been investigated on diverse materials such as polymeric adsorbents, active carbon, zeolite, hydroxyapatite, zirconium phosphate, modified silica, silica-gels (Munsch et al. 2001; Vlasova and Golovkova 2004; Imamura et al. 2003; Krohn and Tsapatsis 2005; Palit and Moulik 2001; El Shafei and Moussa 2001; El Shafei 2002). The promising adsorbents are also ordered mesoporous materials because of their excellent physical and chemical properties (Kresge et al. 1992). These materials have high surface areas, narrow pore size distribution, control
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