Divinylbenzene exchange rates

Chromatographic System Use a liquid chromatograph equipped with a refractive index detector that is maintained at a constant temperature and a 9-mm x 30-cm column packed with a strong cation-exchange resin, about 9 pm in diameter, consisting of sulfonated cross-linked styrene-divinylbenzene copolymer in the calcium form (Aminex HPX-87c, or equivalent). Maintain the column temperature at 85° + 0.5°, and the flow rate of the Mobile Phase at about 0.5 mL/min. Chromatograph the Standard Preparation, and record the peak responses as directed under Procedure. Replicate injections show a relative standard deviation not greater than 2.0%. 

D 17. — J. Seidl, and J. MALiNsrf Ion exchange matrices. XI. Rate of swelling of st3rrene-divinylbenzene-copolymers in relation to their structure. II. Copolymers with increased porosity. Chem. prfimysl 13, 662 (1963). 

Figure 21.22. Separation of amino acids by ion-exchange chromatography. Resin Durrum DC-IA, a sulfonatedpolystyrene-divinylbenzene cation exchanger of dp = S pm. Ten nanomole calibration mixture. Flow rate 70 mljhr. From James R. Benson, Durrum Resin Report No. 5, April, 1973, Durrum Chemical Corp., by permission of Durrum Chemical Corp.

Five years later Hatch and Dillon rediscovered the fact that conventional ion-exchange resins efficiently separate acids from their salts under conditions that exclude normal ion exchange. The strong basic anion-exchange resin Dowex-lx8 (8% divinylbenzene (DVB), 40% water content) was found to function especially well and the investigators decided to introduce acid retardation as a new term. Such separations can be defined as acid retardation separations, since they are based on a preferential absorption of strong acids, which causes the movement of the acid on the bed to be retarded — i.e., slowed down — relative to the movement of the salt [115]. Acid retardation, like ion retardation, can be done at high flow rates, especially at elevated temperatures. These processes have been optimized and since 1976 widely exploited by Eco-Tec Canada [119, 120], as well as by others [121], on the industrial scale. 

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