ASIAN JOURNAL OF CHEMISTRY ASIAN JOURNAL OF CHEMISTRY http://dx.doi.org/10.14233/ajchem.2014.18071 INTRODUCTION Capillary liquid chromatography has been one of the most important recent developments in separation and analysis technology. Capillary liquid chromatography offers several advantages over conventional normal chromatography. The advantages include increased chromatographic resolution, higher efficiency, lower sample and solvent consumption, the ability to analyze and isolate rare compounds of interest, greater mass sensitivity and ease of on-line connection to a mass spec- trometer 1-3 . Traditionally, capillary liquid chromatography uses fused silica capillaries prepared with a variety of stationary phases. This technique appears to be very promising for sepa- rating a wide variety of analytes for different applications 4-10 . However, the successful development of this technique is closely related to the technical challenges associated with manufacturing the column. Monolithic columns have quickly become extremely popular and they have attracted increasing interest as separation media for all chromatographic methods. The unique structure of the monoliths and their ease of preparation offer improved chromatographic performance and favorable properties that Preparation of High Porous Poly(2-ethylhexyl methacrylate-co-ethylene Glycol Dimethacrylate) Monolithic Columns for Fast Separation of Small Molecules HESSA K. AL-SHAMMARI 1 , AHMAD AQEL 2 and ZEID A. ALOTHMAN 2,* 1 Chemistry Department, College of Science, University of Ha'il, P.O. Box 1560, Ha'il, Kingdom of Saudi Arabia 2 Advanced Materials Research Chair, Chemistry Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Kingdom of Saudi Arabia *Corresponding author: Fax: +96 614675989; Tel: +96 614675999; E-mail: zaothman@ksu.edu.sa Received: 23 May 2014; Accepted: 8 September 2014; Published online: 15 November 2014; AJC-16330 This paper describes the fabrication of monolithic materials for use as stationary phases in capillary liquid chromatography. Four columns were synthesized in the confines of 320 μm i.d. and 200 mm long fused-silica capillaries using a single step in situ copolymerization of 2-ethylhexyl methacrylate and ethylene glycol dimethacrylate (EDMA). The polymerization procedure was optimized; ethylene glycol dimethacrylate crosslinker content showed predominant influence on the columns characteristics. Changes of the porous and hydrodynamic properties of the prepared monolithic columns were thoroughly investigated and their morphologies were characterized by examining the scanning electron microscopy images and Fourier transform infrared spectra. A decrease in the porogen to monomer ratio corresponded to smaller microglobules and a lower total porosity. The microglobules had an approximate diameter in the range of 1-2 μm. The total porosities ranged from 73 to 80 % using the retention times of uracil as an unretained marker. The resulting monoliths exhibited good permeability and mechanical stability, while swelling behaviour was observed and discussed. The efficiency and performance towards different sets of analytes were obtained; mixtures of aromatic hydrocarbons and phenolic compounds were successfully separated and evaluated. Fast separations were achieved in less than 5 min for the model compounds. Keywords: Capillary liquid chromatography, Monolithic column, 2-Ethylhexyl methacrylate, Aromatic hydrocarbons, Phenolic compounds. result in high efficiency 11-14 . Hjertén et al. 15 first introduced the use of monoliths with capillary liquid chromatography in 1989 and since that time, monolithic stationary phases have been extensively studied for use in capillary liquid chromato- graphy 16-20 . In addition to the preparation conditions, such as the reaction time and temperature, the chemical and physical properties of the monolithic polymer depend on the type and concentrations of the monomer, crosslinker, porogenic solvent and initiator. Several monoliths, including methacrylate polymers 21-30 , have been widely prepared and studied in the literature. There are several advantages associated with using methacrylate- based polymers as monolithic stationary phases, such as high stability in a wide range of mobile phase pH values (2-12), fast and simple preparation and ease of functionalization. Methacrylate monolithic columns also have various selecti- vities towards monomers with wide ranging polarities 31,32 . EXPERIMENTAL Formic acid, toluene, aminophenol, chlorotoluene and nitrotoluene of analytical grade were purchased from BDH Asian Journal of Chemistry; Vol. 26, No. 23 (2014), 8223-8228