Packings for Size Exclusion Chromatography: Preparation and Some Properties

Abstract

Materials used as packings in size-exclusion chromatography can be divided into organic and inorganic ones. Organic packings include both synthetic and natural products. The preparation of these matrices, the mechanism of porous structure formation, depending on synthesis conditions, as well as the properties of packings, are reviewed.Since the column is the heart of any chromatographic system, the choice of packing greatly affects the success of any analysis. The basic requirements for the packing material for size-exclusion chromatography (SEC) columns include chemical inert ness and minimal adsorption of separated compounds so that the retention may be strictly based on hydrodynamic volume. Further requirements include high porosity which can be either permanent in macroporous resins, or swelling in low-crosslinked polymers. In addition to the chemical properties, the importance of physical pro perties such as the particle size must be stressed to achieve an adequate resolution of the packing. The particles should be spherical and uniform in size to minimize mass transfer limitations. Since the column separation efficiency increases with decreasing particle size, the size should be as small as possible, however, with good flow properties. High-speed, high-resolution chromatography also sets special re quirements for geometrical and mechanical properties. They play a decisive role in the lifetime of the packing and the stability of the flow-rates through the column. It is therefore desirable that all the factors outlined above should be taken into account when choosing the packing. Generally, packings can be divided into universal and those that have a specific effect or "tailor-made" packings. A universal packing covers a broad molecular-weight distribution of the components of an unknown sam ple. Such preliminary assessment allows the subsequent choice of a resin that has the optimum properties for a given separation problem.Chromatographical packings have been already systematically reviewed in many papers and monographs (7-9). The aim of article is to review the synthesis, morphology and other properties of packings which are important for SEC.