It was shown earlier that in serially coupled column systems, not only retention (selectivity) but peak width as well can change and the apparent peak width depends on the order of the columns. A generic equation has been developed to describe the apparent efficiency of serially coupled columns in gradient elution liquid chromatography mode. In a previous work, the theoretical basis for a two-column system was developed and by extending and generalizing this model, it is now possible to predict the apparent peak width for the combination of any column segments in any formats (columns possessing various efficiencies and lengths). (Identical retention and selectivity have been assumed to develop this model.) At the end, column order can be a useful parameter to set the desired efficiency of coupled systems.