The process of  increasing width and concomitant diluting  of the chromatographic band as it moves  down the column. The peak is injected as a  narrow slug and, ideally, each separated  component would be eluted as a narrow  slug of pure compound if not for the  process of band broadening. The measure of band broadening is bandwidth (tw) or,  more correctly, the number of theoretical  plates (N) in the column. Sometimes  called band dispersion or band spreading.