Mobile phase influence intermediate

Enantiomeric forms of proteins are not accessible so that a conceptual reversal of the elution order by switching to the enantiomeric CSP is not feasible. However, in some special ca.ses, the elution order can be influenced by the mobile phase conditions. For example, on an ovomucoid CSP a reversal in elution order of the enantiomers of the ketal tosylate intermediate of azalanstat was observed when the organic modifier was changed from ethanol to acetonitrile. This unusual effect has been attributed to a change in binding domains or recognition sites on the ovomucoid protein as a function of the organic modifier of the mobile phase [ 149. ... 

It is appropriate to emphasize again that mechanisms formulated on the basis of kinetic observations should, whenever possible, be supported by independent evidence, including, for example, (where appropriate) X-ray diffraction data (to recognize phases present and any topotactic relationships [1257]), reactivity studies of any possible (or postulated) intermediates, conductivity measurements (to determine the nature and mobilities of surface species and defects which may participate in reaction), influence on reaction rate of gaseous additives including products which may be adsorbed on active surfaces, microscopic examination (directions of interface advance, particle cracking, etc.), surface area determinations and any other relevant measurements. 

Reasons why reactions of solids may proceed more rapidly in a molten zone than within a crystalline reactant [75], include (i) relaxation of the regular stabilising intracrystalline forces (ii) establishment of a favourable configuration for chemical change may be possible due to mobility in a liquid but inhibited within a rigid crystal stmcture, and (iii) the influences of intermediates and impurities may be greater (or different) in a molten phase. 

However, the density of the medium affects the course of radiolysis in another well-known, and very important way. Long-living reactive intermediates such as free atoms and radicals remain localized for an appreciable period of time in the close neighborhood of the parent activations because of their limited mobility in condensed phase. Hitherto neglected space and time correlations between the individual elementary acts thus begin to influence considerably the subsequent processes. This fact has to be taken into account in the theory of primary processes. 

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