Due to the better understanding of the processes taking place at the surface of the stationary phases, the number of ion-exchange materials for ion chromatography (IC) has increased tremendously over recent years. As a result, the multitude of commercially available columns today with their different selectivities for anion and cation chromatography is almost confusing. Hence, the aim of this article is to describe the different principles determining selectivity and ion-exchange capacity and to classify the various ion-exchange materials accordingly. To ensure a fair comparison of these columns, the selectivity differences are illustrated by showing separations of standards rather than individual samples. Keywords Ion chromatography · Stationary phases · Support materials · Inorganic anions and cations · Organic anions and cations Anion exchangersPolymer-based anion exchangers Styrene/divinylbenzene copolymers, polymethacrylate, and polyvinyl resins are the most important organic polymers that are used as substrate materials in the manufacturing process for polymer-based anion exchangers.

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Irradiation of purine and pyrimidine ribonucleotides in aqueous solution with X-rays (200 kv) results in the formation of intermediate labile phosphate esters which lead to a post-irradiation release of inorganic phosphate. This release of phosphate, which occurs after irradiation in the presence or absence of oxygen, follows a first-order rate law and is strongly base-catalysed. It is suggested that the radiation-induced lability of the nucleotides is due to the formation of activating carbonyl groups in the sugar components, PREVIOUS studies of the action of X-rays (200 kv) on purine and pyrimidine ribonucleotides in aqueous solutions have shown that a number of chemical reactions take place. Both the base and the pentose constituents are attacked, ammonia and inorganic phosphate being formed. Some free base is also liberated but no nucleoside or free pentose is produced. Such chemical changes induced by ionising radiations in dilute aqueous systems are due, in the first instance, to the production of free radicals from the water according to the net process :The radicals thus formed may then react with the solute. Because of the possible rBle of labile phosphate esters in the radiation-induced degradation of nucleic acids in aqueous systems,3 we have studied the effects of X-rays on a number of phosphate esters. The ribonucleotides are of obvious interest from this point of view and in the following we report our observations with adenylic and cytidylic acid, which are typical of purine and pyrimidine ribonucleotides respectively.

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