Overlapping-resolution mapping

A multiresidue analytical method based on sohd-phase extraction enrichment combined with ce has been reported to isolate, recover, and quantitate three sulfonylurea herbicides (chlorsulfuron, chlorimuron, and metasulfuron) from soil samples (105). Optimi2ation for ce separation was achieved using an overlapping resolution map scheme. The recovery of each herbicide was >80% and the limit of detection was 10 ppb (see Soil chemistry of pesticides). 

Ng et al. [107] described a simple and rapid systematic optimization scheme, known as overlapping resolution mapping scheme, which make use of nine... 

Once the retention surfaces are known, any criterion may in principle be used to calculate the response surface and to locate the optimum composition. One of the criteria used by Glajch et al. is the threshold minimum resolution criterion (section 4.3.3). This is done by means of a graphical procedure, referred to as overlapping resolution mapping or ORM. This procedure involves the location of areas in the triangle where the resolution Rs exceeds a certain threshold value. This is repeated for all pairs of solutes and the results are combined to form a single figure. 

An example of the procedure and the resulting overlapping resolution map is shown in figures 5.24 and 5.25. Because of the simple retention surfaces, each pair of peaks yields... 

Figure 5.24 Overlapping resolution maps for eight relevant solute pairs for the separation of nine substituted naphthalenes. Figure taken from Glajch et al. [542]. Reprinted with permission.

Figure 5.25 Overlapping resolution map (ORM) for all nine solutes of the sample in figure 5.24. Figure 5.25 is the result of superimposing all eight triangles of figure 5.24. Figure taken from Glajch et I542J. Reprinted with permission.

Optimization of separations, 56 Orientation forces, 43, 44 Overlapping resolution mapping, 213-218... 

Figure 9.34. Overlapping resolution map (ORM) combining the data in Figure 9.33. Reprinted with permission from ref. 65.

For multivariable optimization as in the present case, so-called overlapping-resolution mapping (ORM) can be a useful approach to computer-assisted optimization of solvent selectivity 20,46). This will be... 

Fig. 25. Overlapping resolution maps for sample of Fig. 24 (a) Band pair 6-8 (b) all band pairs.

The present model predicts how solvent selectivity will vary with mobile-phase composition, and this allows the selection of extreme solvents for maximum differences in selectivity. This information plus the ability to calculate solvent strength versus composition of the mobile phase then allows development of a general strategy for optimizing retention of any sample, so as to maximize resolution. This four-solvent approach can be further refined by use of computer-assisted procedures, such as the overlapping-resolution-mapping technique. 

Fig. 1.24. Overlapping resolution map for the separation of a four-component mixture with optimisation of tw

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