High resolution, ideal conditions

Much of the research on the l.c. of carbohydrates has focused on analytical, rather than preparative, aspects. In reality, however, the conditions found in the majority of l.c. methods, namely, no sample derivatization, high-resolution separations, and nondestructive detection-techniques, are ideal for the preparation of pure molecules. Thus, most of the analytical l.c. methods previously described can also be used to isolate small quantities of pure compounds. This Section will cover the use of analytical-scale equipment for preparative applications, as well as the use of large-scale and dedicated preparative instruments for this purpose. Prior to discussion of these applications, a general overview of the preparative l.c. of carbohydrates will be given. 

With any resist, the ideal conditions for obtaining high resolution and good linewidth control are a flat surface and a thin resist (<400 nm). The flat surface means that the resist will have very little variation in thickness and, as a result, there will be little variation in resist linewidth. However linewidth variations stemming from resist thickness variations do occur when lines traverse a step as a result of exposure and development effects. Indeed, such... 

Only a high-resolution structural method that overcomes the difficulties of deconvoluting multiple, spatially highly overlapping structures (Fig. 4) is likely to be able to accurately answer this question. The spectral overlap problem is a principal one since even under ideal conditions it is not possible to achieve occupancies of the K or L intermediate higher than about 50% and 70%, respectively, because of the extensive spectral overlap between the ground state and both the K and the L intermediate (Amax differences of +22 nm and —28 nm, respectively) (Balashov and Ebrey, 2001). 

In the present case after a rough test no major deviations from the ideal DlP/Au model system could be detected but further, more detailed studies using high-resolution electron spectroscopies with synchrotron radiation and additional morphological techniques such as AFM may reveal subtle differences. These will be performed after optimisation of the lift-off technique which is presently under way and will be applied completely under UHV conditions, thus allowing the minimisation of spurious influences. Then further investigations on buried interfaces combining XPS, UPS, IPES, NEXAFS, and AFM will be performed on the present and several other systems which are a matter of present research. 

By the 1980s most of the aluminosilicate zeolites currently used industrially were known, and the emphasis shifted to the study of these materials using a range of powerful new techniques that came of age at this time. These included, in particular, solid state NMR, X-ray and neutron powder diffraction analysis, high resolution electron microscopy and computational methods. All were ideal for the study of structural details of solids that were rarely available, and never used in industrial applications, other than as microcrystalline powders. All these techniques are applicable to the bulk of the solid - this in turn makes up the (internal) surface, which is accessible to adsorbed molecules. Since the techniques are able to operate under any conditions of gas pressure, they may be used to extract structural details in situ under the operating conditions of ion exchange, adsorption and catalysis. In particular, zeolitic systems have proved ideal for the study, understanding and subsequent improvement of solid acid catalysts. 

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