Multisegment gradients

For complex samples, segmented gradients with varying steepness may provide the best resolution across the separation. However, multisegment gradients often have problems with precision and transferability. 

Therefore, selectivity optimization, is in principle to be preferred over multisegment gradients. In GC, where selectivity optimization is not attractive because of the requirement to use different columns, one may wish to resort to multisegment gradients for practical reasons. In LC, where selectivity optimization is readily possible by using different modifiers in the mobile phase, multisegment gradients are of little practical interest. 

Simplex optimization of the primary (program) parameters in programmed temperature GC analysis has been demonstrated [612]. A systematic sequential search [613] may be used as an alternative. The Simplex method may be used to optimize a limited number of program parameters, whereas the latter approach was developed for the optimization of multisegment gradients. The use of interpretive methods has so far only been suggested [614,615]. 

The exact procedure in which the multisegment gradient is built up from the optimum... 

Selectivity optimization of simple, continuous gradients will be easier than the optimization of complex multisegment programs, because there are bound to be serious... 

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