How is Dispersion Measured?

How is Dispersion Measured?

Dispersion can be measured by injecting a sample of acetone onto a zero dwell volume (ZDV) union to measure the extra column band broadening effect. The method conditions are described below in Figure 1, with an example of two systems with different system volumes and bandwidths.

To determine the instrument bandwidth, the retention time (t_R) and efficiency at half height (N) should be recorded. These can be inserted into Eq. 1 to calculate sigma (σ), which in turn can calculate instrument bandwidth (4σ, Eq. 2). Consequently, the system volume can also be determined by this test by multiplying the average retention time of acetone by the flow rate (Eq. 3).

Figure Operating conditions for system dispersion and example chromatograms of two different systems.