Triangulation and Other Algorithmic Methods

FIGURE 2.4 Chromatograms of 11 lignans separated on a C g column using water/oiganic gradients. 

solvents are classified as to their hydrogen bond acidity (a), hydrogen bond basicity (fi) and polarizability/dipolarity ( c ). Although a mathematical rq iesenta-tion of the relationship between k and a, ji, and n exists as [56-58] 

There are two basic types of triangulation methods. One is based on a mathematical representation of solvent selectivity and the other is based on general chromatographic knowledge. Nonetheless, these optimization processes use the same overall strategy simultaneously alter three variables that affect retention (here the composi- 

FIGURE 2.5 (a) An example of a mobile phase triangle with pure solvents as apices. Seven experiments are used in the initial optimization each apex and points 1 to 4. (b) The second iteration of the optimization process. Four experiments are run points S to 8. 

FIGURE 2.6 A plot of the results for the second iteration. Here Z may represent the separation factor, a, between any set of peaks or a parameter that combines the separation with overall retention time. For example, afier designating a minimum acceptable a, the parameter Z = a X (I/O where is the retention time of the latest-eluting peak. Z increases as a increases (resolution gets better) and/or total elution time decreases (sample throughput increases). 

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