title: Synthesis, characterization, and evaluation of a superficially porous particle with unique, elongated pore channels normal to the surface.
abstract: In recent years, superficially porous particles (SPPs) have drawn great interest because of their special particle characteristics and improvement in separation efficiency. Superficially porous particles are currently manufactured by adding silica nanoparticles onto solid cores using either a multistep multilayer process or one-step coacervation process. The pore size is mainly controlled by the size of the silica nanoparticles and the tortuous pore channel geometry is determined by how those nanoparticles randomly aggregate. Such tortuous pore structure is also similar to that of all totally porous particles used in HPLC today. In this article, we report on the development of a next generation superficially porous particle with a unique pore structure that includes a thinner shell thickness and ordered pore channels oriented normal to the particle surface. The method of making the new superficially porous particles is a process called pseudomorphic transformation (PMT), which is a form of micelle templating. Porosity is no longer controlled by randomly aggregated nanoparticles but rather by micelles that have an ordered liquid crystal structure. The new particle possesses many advantages such as a narrower particle size distribution, thinner porous layer with high surface area and, most importantly, highly ordered, non-tortuous pore channels oriented normal to the particle surface. This PMT process has been applied to make 1.8-5.1μm SPPs with pore size controlled around 75Å and surface area around 100m(2)/g. All particles with different sizes show the same unique pore structure with tunable pore size and shell thickness. The impact of the novel pore structure on the performance of these particles is characterized by measuring van Deemter curves and constructing kinetic plots. Reduced plate heights as low as 1.0 have been achieved on conventional LC instruments. This indicates higher efficiency of such particles compared to conventional totally porous and superficially porous particles.
authors.affiliation: Agilent Technologies, Inc., 2850 Centerville Road, Wilmington, DE 19808, USA. Electronic address: ta-chen_wei@agilent.com.
authors.forename: Ta-Chen
authors.initials: TC
authors.lastname: Wei
authors.affiliation: Agilent Technologies, Inc., 2850 Centerville Road, Wilmington, DE 19808, USA. Electronic address: anne_brooks@agilent.com.
authors.forename: Anne
authors.initials: A
authors.lastname: Mack
authors.affiliation: Agilent Technologies, Inc., 2850 Centerville Road, Wilmington, DE 19808, USA. Electronic address: wu_chen@agilent.com.
authors.forename: Wu
authors.initials: W
authors.lastname: Chen
authors.affiliation: Agilent Technologies, Inc., 2850 Centerville Road, Wilmington, DE 19808, USA. Electronic address: jia_liu@agilent.com.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: Agilent Technologies R&D and Marketing GmbH, Hewlett Packard-Strasse 8, Waldbronn 76337, Germany. Electronic address: monika_dittmann@agilent.com.
authors.forename: Monika
authors.initials: M
authors.lastname: Dittmann
authors.affiliation: Agilent Technologies, Inc., 2850 Centerville Road, Wilmington, DE 19808, USA. Electronic address: xiaoli_wang@agilent.com.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Wang
authors.affiliation: Agilent Technologies, Inc., 2850 Centerville Road, Wilmington, DE 19808, USA. Electronic address: bill_barber@agilent.com.
authors.forename: William E
authors.initials: WE
authors.lastname: Barber
mesh_terms: D002623:Chemistry Techniques, Analytical / Q000379:methods*; D002851:Chromatography, High Pressure Liquid; D007700:Kinetics; D008823:Micelles; D010316:Particle Size; D016062:Porosity; D015203:Reproducibility of Results; D012822:Silicon Dioxide / Q000138:chemical synthesis* / Q000737:chemistry / Q000592:standards
chemical_list: D008823:Micelles; D012822:Silicon Dioxide
keywords: Highly ordered straight pores; Micelle templating; Pseudomorphic transformation; Radially oriented pores; Superficially porous particles; Ultrahigh column efficiency