Optimization of programmed solvent LC

The (primary) program parameters may be used to optimize the separation in programmed solvent LC in a non-selective way. Since this involves optimization of the 

The most useful secondary parameter for the optimization of the selectivity in programmed solvent LC is the nature of the modifter(s) in the mobile phase. The selectivity can be varied by selecting various solvents (pure solvents for binary or ternary gradients mixed solvents for pseudo-binary gradients). Analogous to the situation in isocratic LC, it is possible to use different modifiers (and hence to obtain different selectivity) while optimum retention conditions are maintained for all solutes. This possibility to optimize the selectivity in programmed solvent LC will be discussed below. 

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For the optimization of programmed solvent LC the Sentinel method starts by establishing a suitable binary methanol-water gradient. The approach of Snyder described above may be used for this purpose. For example [627], a gradient from 20 to 100% methanol (in water) in 20 minutes may be the result. 

Figure 6.14 Result of a Sentinel optimization of programmed solvent LC. Experimental design according to figure 6.13 and table 6.4. (a) Predicted optimum linear gradient and (b) chromatogram obtained with the optimum linear gradient. Stationary phase Zorbax alkyl silica.

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