Modern (U)HPLC columns with plate heights as low as 3-4 μm generate plate numbers on the order of 25 000-30 000 plates / 10 cm.For a 2.1x50 mm columns the peak variance is ca.5 μl2 (k =2).The separation efficiency of such columns can be easily compromised by external contributions to dispersion stemming from connection capillaries, auto-samplers and detection cells.In order to understand the impact of the individual system components such as connection capillaries or detector cells, the authors have set up a system that allows measuring the dispersion of these components independent of each other.This system also allows the determination of column-related peak variance keeping external contributions at an ultra-low level.