Single Chromatographic Columns

Chromatographic fixed-bed reactors consists of a single chromatographic column containing a solid phase on which adsorption and reaction take place. Normally a pulse of reactant is injected into the reactor and, while traveling through the reactor, simultaneous conversion and separation take place (Fig. 3). Since an extensive overview of the models and applications of this type of reactor was presented by Sardin et al. [ 132], only a few recent results will be discussed here. Most of the practical applications have been based on gas-liquid systems, which are not applicable for the enzyme reactions, but a few reactions were also reported in the liquid phase. One of these studies, performed by Mazzotti and co-workers [ 141 ], analyzed the esterification of acetic acid into ethyl acetate according to the reaction ... 

The principle of reactive chromatography can be easily explained using a simple reversible reaction of type A o B + C. Looking at a single chromatographic column filled with a stationary phase which serves as a selective adsorbent and as a heterogeneous catalyst, the development of a pulse of A injected into the continuous eluent stream is shown in Fig. 6.1. 

Monolithic structures enable two additional interesting features. Because of their defined dimension, several monolithic disks can be stacked together forming a single chromatographic column. Such a column has much better performance in comparison to a group of several columns... 

The second approach consisted in the separation of CLA isomers as the p-methoxyphenacyl esters with dichloromethane/hexane/acetonitrile mixtures as the mobile phase (14). In this instance, only a single chromatographic column was required. Because detection was by the absorbance of the p-methoxyphenacyl moiety at 270 nm, aU fatty acids were detected and quantified, not simply the conjugated dienes. Finally, good resolution of CLA as the free acids has recently been reported, with hexane/acetonitrile/acetic acid mixtures as the mobile phase with detection of the conjugated double bonds at 234 nm (15). This procedure may be of special value for commercial CLA samples supplied as the free adds because no derivatization step is required. 

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