Symmetrical response surface designs

Also in situations where it is in practice impossible to perform one or more of the planned experiments from a symmetrical response surface design, irregular experimental areas remain and are to be explored. A situation similar to Figure 2.10a (see further) is obtained. For example, when considering the variables pH and percentage organic modifier in the mobile phase or the background electrolyte, it can happen that one of the compounds to be analyzed does not dissolve anymore and/or that conditions are created where no elution occurs. 

A.2.3. Example of an Applied Response Surface Design. In the optimization phase of the development of a CE method for the chiral enantio-separation of a nonsteroidal anti-inflammatory drug (28), a circumscribed CCD was performed. The applied symmetrical response surface design is as shown in Table 2.14, with a = 2 f = 1.68. The center point (experiment 15 in Table 2.14) was replicated five times (experiments 15-19). 

Response surface designs can be divided into symmetrical and asymmetrical designs (7). The first type examines the factors in a symmetrical experimental domain, while the second can be chosen when an asymmetrical experimental domain is to be examined. 

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