Author: RPW Scott
Book:Extra Column Dispersion
Section:EC-Dispersion Rapid-Separations
mixture contains components that extend over a wide polarity or molecular weight range then gradient elution development will be necessary and fast gradients are almost impossible to form with conventional LC solvent programmers. As a consequence, for high speed gradient separations, a unique procedure must be used in conjunction with specially designed apparatus. The solution to the problem of fast gradient generation is to employ a preformed gradient a concept that was first introduced by Snyder and Saunders (13) as long ago as 1969. A diagram of a gradient preformer is shown in figure 27. In the particular apparatus that was used to provide the fast analyses that are described below the required gradient was formed in a column 25 cm long, 4.6 mm I.D. packed with glass beads 40 mm in diameter


