What is dispersion?

What is Dispersion?

Dispersion is a measure of analyte band broadening between the injector and detector, excluding the contribution from the column. As a sample is injected into the flow path, the analyte band begins to spread by both intra- and extra-column effects. The intra-column effects are dictated by the efficiency of the packed column bed. A poorly packed column will result in a large degree of band spreading, resulting in wide, inefficient peaks. The extra-column band broadening is a result of the injector, tubing, valves and detector in the LC system. As such, dispersion is one of the fundamental tests which should be performed to characterise an LC system.

Historically for HPLC analysis, the intra-column effects had the greatest impact on band spreading. However, with the changing trend towards UHPLC, narrow bore ID and smaller particle sizes, the impact of extra-column band broadening is far more noticeable and detrimental to the separation. Therefore, it is important to experimentally measure the LC’s dispersion.