Choice of Preparative LC Technology

From a process-engineering point of view, there is now a better understanding of the development of concentration profiles in chromatographic columns under overloaded conditions available. This includes in particular the quantitative description of displacement and tag-along effects caused by competitive adsorption. Since it is now possible (as mentioned before) to simulate concentration profiles on a personal computer, the choice of the appropriate mode 

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Boron clusters are effective and unusual structural elements for designing calamitic and bent-core mesogens. Their structural and electronic diversity combined with judicious choice of substituents makes it possible to address fundamental aspects of liquid crystal research, to design LCs with unusual properties, and to prepare technologically important materials. Properties of these formally inorganic-organic hybrid mesogens, such as photophysical behavior, polarity, and phase structure, can be tuned by judicious choice of the cluster and substituents. 

Because the instability of the N-oxide metabolite, which was subjected to decomposition during sample preparation (solvent evaporation during offline SPE), online SPE LC/MS became the method of choice for the application. Hsieh et al. (2004) built a system with two TFC cartridges and one analytical column, and another system with two TFC cartridges and two analytical columns for GLP quantitative bioanalysis of drug candidates. A Turbo C18 (50 x 1.0 mm, 5 /.mi, Cohesive Technologies), an Xterra MS C18 (30 x 2.0 mm, 2.5 /mi), and a guard column were used. Protein precipitation preceded injection. The cycle times for the two systems were 0.8 and 0.4 min. 

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