Time corrected resolution products

Required analysis times and time-corrected resolution products for the three chromatograms of figure 4.12. Constant flow rate and diameter (of open columns or particles) (i.e. constant f,d conditions) have been assumed. 

On the other hand, if it is planned that the optimization column can be a different length (typically shorter) than the final separation column, another CRF can be used the time-corrected normalized resolution-product, r tc, given by... 

Shown in Figure 5 are the calculated response surfaces for both the threshold separation (CRF-4) and time-corrected normalized resolution product (CRF-5). As expected, the threshold response surface is discontinuous, with 3 local optima in contrast, the response surface for CRF-5 is smooth, with no apparent local optima. 

Figure 5. Comparison of the threshold separation and time-corrected, normalized, resolution-product response surfaces for the eight component sample (Table ID). Response surfaces calculated via equations 9 and 10 using the isothermal retention surfaces of Figure 4.

The time-corrected normalized resolution product now becomes ... 

Since the early times of stereochemistry, the phenomena related to chirality ( dis-symetrie moleculaire, as originally stated by Pasteur) have been treated or referred to as enantiomericaUy pure compounds. For a long time the measurement of specific rotations has been the only tool to evaluate the enantiomer distribution of an enantioimpure sample hence the expressions optical purity and optical antipodes. The usefulness of chiral assistance (natural products, circularly polarized light, etc.) for the preparation of optically active compounds, by either resolution or asymmetric synthesis, has been recognized by Pasteur, Le Bel, and van t Hoff. The first chiral auxiliaries selected for asymmetric synthesis were alkaloids such as quinine or some terpenes. Natural products with several asymmetric centers are usually enantiopure or close to 100% ee. With the necessity to devise new routes to enantiopure compounds, many simple or complex auxiliaries have been prepared from natural products or from resolved materials. Often the authors tried to get the highest enantiomeric excess values possible for the chiral auxiliaries before using them for asymmetric reactions. When a chiral reagent or catalyst could not be prepared enantiomericaUy pure, the enantiomeric excess (ee) of the product was assumed to be a minimum value or was corrected by the ee of the chiral auxiliary. The experimental data measured by polarimetry or spectroscopic methods are conveniently expressed by enantiomeric excess and enantiomeric... 

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