Comparison of Different Reversed-Phase Packing Materials Based on Higher Organic Hybrid Particles
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1007-S04-04
Comparison of Different Reversed-Phase Packing Materials Based on Higher Organic Hybrid Particles Nicole L. Lawrence, Kevin D. Wyndham, Kenneth H. Glose, Jim T. Cook, Darryl W. Brousmiche, Pamela C. Iraneta, Bonnie A. Alden, Cheryl A. Boissel, and Thomas H. Walter Waters Corporation, 34 Maple Street, Milford, MA, 01757 ABSTRACT As part of our ongoing exploration into the field of hybrid organic/inorganic particles as HPLC packing materials, we have recently evaluated the use of porous particles synthesized from the co-condensation of ethylene-bridged alkoxysilanes with tetraethoxysilane [1,2]. By employing 4-100 mol% of hybrid organic/inorganic groups (i.e., O1.5SiCH2CH2SiO1.5) to 960 mol% inorganic groups (i.e., SiO2), novel hybrid particles have been prepared and shown to be excellent materials for the preparation of efficient and chemically resilient reversed-phase packing materials. INTRODUCTION Since our commercialization of reversed-phase high performance liquid chromatography columns based on hybrid particles in 1999, our group has continued to research the synthesis and chromatographic performance of several different organic/inorganic hybrid particle formulations (e.g., (R1SiO1.5)a(O1.5Si-R2-SiO1.5)b(SiO2)c where R1 and R2 are terminal or bridging organofunctional groups). Hybrid particles have been shown to be effective packing materials for reverse-phase HPLC, providing excellent chemical stability when used at elevated pH. The surface silanols of these materials can be modified using chlorosilanes (e.g., C18H37SiCl3) [1]. Alternatively, hybrid particles containing synthetically relevant organofunctional groups (e.g., where R1 contains an alcohol, bromine or alkene) can be modified using a variety of synthetic transformations [3]. In this paper, we explore the synthesis and characterization of reversed-phased packing materials based on different molar ratios of 1,2-bis(triethoxysilyl)ethane (BTEE) and tetraethoxysilane (TEOS) to yield hybrid particles having the formula (O1.5SiCH2CH2SiO1.5)x(SiO2)1-x (where x = 0.04-1). We will also evaluate the reversed-phase chromatographic performance of these new packing materials and compare these results with conventional silica-based chromatographic materials. EXPERIMENTAL Instrumentation. Combustion analyses were obtained on a CE-440 Elemental Analyzer (Exeter Analytical Inc.). The specific surface areas (SSA), specific pore volumes (SPV) and the average pore diameters (APD) of these materials were measured using the multi-point N2 sorption method (Micromeritics ASAP 2400). The SSA was calculated using the BET (Brunauer, Emmet, and Teller) method, the SPV was the single point value determined for P/P0 > 0.98 and the APD was calculated from the desorption leg of the isotherm using the BJH method. Particle sizes were measured using a Beckman Coulter Multisizer 3 analyzer (30-µm aperture,
70,000 counts). Multinuclear (13C, 29Si) CP-MAS NMR spectra were obtained using a Bruker Instruments Avance-300 spectrometer (7 mm double broad band probe). The HPLC
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