An Extended Range of Columns for Aqueous Size Exclusion Chromatography

1. An Extended Range of Columns for Aqueous Size Exclusion Chromatography Inspiring Excellence™ Greg Saunders, Graham Cleaver and Ben MacCreath, Varian, Inc., Church Stretton, Shropshire SY6 6AX, UK PL aquagel-OH Range for Aqueous SEC The use of SEC for the analysis of aqueous polymers is of growing interest. However, this application area is challenging due to the number of ionic and hydrophobic interactions that can occur when analyzing water soluble materials. PL aquagel-OH columns have been specifically designed to allow the analysis of materials of this kind. Simple modification of the eluent minimizes interactions and ensures that pure size exclusion chromatography is obtained. Introduction Size exclusion chromatography (SEC), also known as gel permeation chromatography (GPC), is an important analytical technique in the field of polymer analysis. Using SEC, samples of polymer are separated on the basis of size in solution. Assuming an appropriate calibration is performed or specific information-rich detectors are selected, the size separation can be converted into a molecular weight separation - key information in describing the physical behavior of the polymer. Aqueous SEC is used for the analysis of water-soluble polymers. Recently, there has been increasing interest in this area as the development of biodegradable and environmentally friendly materials has grown. Typically, SEC columns for aqueous applications require packing materials with highly hydrophilic surfaces that are compatible with water and buffers. Particle sizes must be tailored to allow high-resolution separations to be performed without undue increase in column backpressure that can lead to shearing effects and can reduce the column lifetime. Finally, as the range of applications grows a very large array of columns is required to cover all possible sample types across the range. This poster describes an extensive family of columns for aqueous size exclusion chromatography. The columns are packed with materials of high hydrophilicity to ensure pure SEC is obtained for the widest range of samples, including anionic, cationic and hydrophobic types. Being available in many particle and pore sizes, this newly completed range of columns represents a versatile solution to aqueous SEC. Typical Standard Separations The PL aquagel-OH range of columns can be calibrated in aqueous eluents by the use of polyethylene glycol and oxide (PEG/PEO) standards, or with pullulan polysaccharaides. PEG/PEO standards are suitable for a wide range of applications, whereas the polysaccharide standards are more suited to the analysis of biological sugar-based materials as they are similar in structure and therefore give more realistic results. Size Exclusion Chromatography SEC is a technique used for the separation of macromolecules on the basis of their size in solution. A sample is introduced into a flow of solvent passing through a column packed with porous beads. As the molecules pass down the column they are able to diffuse in and out of the pores, dependent on their relative dimensions. As a result, smaller molecules, (lower molecular weight) are retarded in eluting from the column compared to larger molecules (higher molecular weight). Thus a size separation is obtained. • Features of the PL aquagel-OH range: • pH range 2 – 10 • Compatible with 50% methanol • High mechanical stability • 8 μm columns for analytical work • 15 µm for high viscosity polymers • 5 µm for high resolution analysis 1 3 5 7 Characteristics of the full PL aquagel-OH Range Typical applications The PL aquagel-OH range of columns covers applications across the molecular weight resolving range. Heparin is a highly-sulfated glycosaminoglycan with a low molecular weight which acts as an anticoagulant. The molecular weight of Heparin influences the clotting of the material. PL aquagel-OH columns may be used to distinguish different batches of this material. Pectin is a structural polysaccharide found in the walls of cells. It is extracted from citrus fruits and used as a gelling agent in food. Molecular weight is a key parameter of this material, controlling the viscosity properties. Chitosan is a polysaccharide produced from chitin, the main component of crab shells. Chitosan has received interest due to it’s susceptibility to biodegradation. A cationic material, chitosan must be dissolved in concentrated acid for analysis and must be analyzed at low pH to obtain good chromatography. Polyacrylamide is a synthetic polymer that has uses as a thickening agent and in gel electrophoresis. Generally a high molecular weight material, the analysis of polyacrylamide requires large particle size columns due to the viscosity of the material. Hyaluronic acid is a naturally occurring polysaccharide that is extracted from the combs of roosters. Used in eye surgery due to its superior viscosity properties, the molecular weight distribution is critical to the medical application of this material. Summary The analysis of water-soluble polymers by SEC is difficult due to the number of ionic and hydrophobic polymers that can be dissolved in water. The PL aquagel-OH column range is an extensive selection of columns specifically designed for the analysis of water-soluble polymers. Available in a range of pore and particle sizes, the PL aquagel-OH range provide solutions for all aqueous SEC appications. 2 6 4 8