Gradient separations retention time

Retention time in a Unear-gradient separation (tj can be expressed as foUow ... 

Figure 4 Crossover of peak retention times as a function of gradient rate in the separation of peptides. (Previously unpublished data are drawn from Swadesh, J. K., Tryptic fingerprinting on a poly(styrene-divinyl benzene) reversed phase column, /. Chromatogr., 512, 3215, 1990.92)...

A typical HPLC separation using a 15-cm column of 15,000 theoretical plates produces peak capacity (Giddings, 1991) of about 80-100 under isocratic conditions and up to 150 under gradient conditions in 1 h(Eq. 7.3, n peak capacity, A number of theoretical plates of a column, and fR and t retention time of the last and the first peak of the chromatogram, respectively). An increase in the number of separated peaks per unit time can be achieved by increased separation speed made possible by monolithic silica columns (Deng et al., 2002 Volmer et al., 2002). This has also been shown for peptides and proteins (Minakuchi et al., 1998 Leinweber et al., 2003). 

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