title: Polar silica-based stationary phases. Part I - Singly and doubly layered sorbents consisting of TRIS-silica and chondroitin sulfate A-TRIS-silica for hydrophilic interaction liquid chromatography.
abstract: Two polar silica bonded stationary phases were prepared by first functionalizing the silica surface with γ-glycidoxypropyltrimethoxysilane, which was then reacted with TRIS to yield a polyhydroxy surface that also has secondary amine functionalities. This step produced the singly layered TRIS-silica column, a cationic hydrophilic column. The TRIS-silica surface was further coated with a layer of chondroitin sulfate A (CSA) yielding the doubly layered hydrophilic CSA-TRIS-silica column. The adsorbed CSA layer provided enhanced hydrophilicity and multi-mode interactions with polar solutes leading to different retention behavior and selectivity compared to the singly layered TRIS-silica column. The anionic sulfate and carboxylate groups in the CSA coating are electrostatically attracted by the cationic TRIS-silica surface yielding a relatively stable physically anchored CSA layer under HILIC elution conditions. The CSA-TRIS-silica column exhibited dual cationic and anionic character with mobile phases at pH ∼3.0 and pH > 4.5, respectively. When comparing solute retention observed on both columns under identical elution conditions, the k values of neutral and cationic solutes were significantly higher on the more hydrophilic doubly layered CSA-TRIS-silica column whereas anionic solutes showed lower k values due to the electrostatic repulsion from the CSA layer.
authors.affiliation: Department of Chemistry, Oklahoma State University, Stillwater, OK, USA.
authors.forename: Renuka
authors.initials: R
authors.lastname: Rathnasekara
authors.affiliation: Department of Chemistry, Oklahoma State University, Stillwater, OK, USA.
authors.forename: Ziad
authors.initials: Z
authors.lastname: El Rassi
mesh_terms: D000327:Adsorption; D000838:Anions; D002809:Chondroitin Sulfates / Q000737:chemistry*; D002853:Chromatography, Liquid / Q000379:methods*; D057927:Hydrophobic and Hydrophilic Interactions; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D000838:Anions; D012821:Silanes; C039462:gamma-glycidoxypropyltrimethoxysilane; D012822:Silicon Dioxide; D002809:Chondroitin Sulfates
keywords: Chondroitin sulfate A-TRIS-silica; Dansyl amino acids; Derivatized sugars; Hydrophilic interaction liquid chromatography; Nucleic acids; Phenoxy acid herbicides; TRIS-silica