Application of Gel Chromatography*

INTRODUCTION The term Gel Chromatography refers to the process of separation of solutes caused by the passage of a solution through a column filled with a porous gel. The dissolved particles may enter the pores fully or partially or they may remain completely excluded. This results in a sorting out of the dissolved particles according to their size, so that the largest particles migrate with the highest rate. The procedure was applied in about 1960 to aqueous solvents' with great success and to organic solvents2 with limited success for the separation of polymers and was named gel filtration. Crosslinked dextran proved to be a very good porous gel. After a few years a highly crosslinked polystyrene3 became available as a gel for organic solvents, which resulted in a breakthrough of this separation technique, here named Gel Permeation Chromatography, as regards its application to synthetic polymers. As in the title of Determann's book4, the term Gel Chromatography describes a separation process on porous gels. The term Chromatography refers to the experimental procedure and not to the micro mechanism. As with most of the chromatographic techniques applied to polymers, the classical chromatographic effect due to interactions with the surface of the bed material is quite undesirable. Every adsorption-desorption step complicates the chromatographic separation of polymers. The numerous review articles on gel chromatography published so far can be divided roughly according to the solvents used5 13• Those for aqueous solvents deal mainly with biopolymers, whereas those for organic solvents are concerned mainly with synthetic polymers'4—'6. The recent monograph of Determann4 covers both types of solvent and polymer and gives an excellent description of the situation in gel chromatography at the end of 1966. This presentation is likewise a review and covers also the possibilities of gel chromatography in analytical and preparative procedures. It will concentrate on synthetic polymers in organic solvents, since there are certainly more unsolved problems with polydisperse threadlike polymer compounds than with monomolecular biopolymers of globular form. This paper is divided into two sections. The first treats the experimental details, while the second handles particularly the evaluation of the experiments. Finally, the preparative possibilities of this method are briefly discussed.