Resolution examples

Mixing the additive in the eluent used as a mobile phase can also modify the chromatographic system (dynamic modification), but the use of modified adsorbents has led to an improvement of resolution. Example works include that by Armstrong and Zhou [11], who used a macrocyclic antibiotic as the chiral selector for enantiomeric separations of acids, racemic drugs, and dansyl amino acid on biphenyl-bonded silica. 

Fig. 6. Finite interferogram and resolution. (Example Three narrow lines of different intensities) upper infinite interferogram I (v) and corresponding spectrum middle finite interfero-...

In 1980, Sindorf and Maciel " published the first high-resolution example of the use of X CP for surface-selective X detection in a demonstration of H- Si CP in silica gel. Since that time, Si CP has remained the most popular application of this strategy, although there has been significant success with applications to other types of systems. Figure 34.2 shows typical Si spectra of silica gel and related samples obtained by CP-MAS and direct polarization (DP) MAS (based on Si spin-lattice relaxation, not CP). 

All five major chiral stationary phases have a very wide range of applications. Nevertheless, the selectivity that they achieve is sometimes limited and the separation ratios of the enantiomers small. As a consequence, relatively high efficiencies are usually necessary to achieve the desired resolution. Examples of the use of the popular protein stationary phases are the separation of the Verapamil isomers, and the epibatidine and vamicamide enantiomers. These chiral stationary phases have also been used to separate optical isomers of a leukotriene antagonist. The Pirkle chiral stationary phases are also very well-liked as... 

Correlative microscopy involves multiple separate microscopy platforms, which are correlated to view the same exact structure of interest with complimentary information [10]. Such systems allow structure-function relationships to be determined at high resolutions. Examples of correlative microscopy include light and electron microscopy, light and atomic force microscopy, immunocytochemistry, and histochemistry, etc. 

As mentioned above, there are several cases of protein dioxygen-copper adducts which have been characterized only by spectroscopy (i.e., tyrosinase) and/or protein x-ray crystallography. The latter cases include oxyhemocyanins, and lower resolution examples are reported for amine oxidase and cytochrome c oxidase. Far more detailed structures are now available for small molecule synthetic complexes, as described below. 

The mass resolution example of P in Si involves an atomic ion and a molecular ion and there are instruments capable of resolving the two. There are instances where the isotope of one element has the same nominal mass of another element and much higher resolving power is required—beyond the capabilities of the commercial instruments. In some cases, it may be possible to use another isotope if the element of interest has multiple isotopes. 

S)-14 (98% ee) was formed in the 38C2-catalyzed forward-aldol reaction (Table 6.1). The recovered aldols were highly enantiomerically enriched by the aldolase antibody-catalyzed kinetic resolution examples include secondary aldols 14, 17, 21, and 32-35, and tertiary aldols 36-40 (Tables 6.2 and 6.3). Kinetic resolution with antibody 38C2 usually afforded higher enantiomeric excess for the recovered aldols than the forward aldol reactions, because one enantiomer was completely consumed in the resolution. For example, (S)-32 was obtained in >99% ee by 38C2-catalyzed kinetic resolution after 67% conversion whereas in the 38C2-catalyzed forward aldol reaction (R)-32 was obtained in 58% ee. 

---