The polydispersity index (PDI) is an indicator of the heterogeneity of particle sizes in the sample and is derived from fitting the autocorrelation function. If particles in the population are uniform, the resulting size distribution will be narrow and the PDI small, determining that the sample is monodisperse. For heterogeneous particle populations, the size distribution will be broader and the PDI increases, determining that the sample is polydisperse. There are several important thresholds of PDI to be aware of:

PR.Panta Control outputs a single PDI along with a single hydrodynamic radius for the cumulant model and the PDI and hydrodynamic radii for up to three discreet peaks for the size distribution model. 

Since the calculation of the PDI differs between the two fitting models, the output PDI values may differ as well. 

In addition, PR.Panta Control uses the cumulant PDI along with the cumulant rH for automatic quality checks to help decide which sizing results should be considered for reporting. The results of the quality checks for each acquisition can be found in the acquisition details tab.

Be aware that scattering data is only available if data was generated with measurement types supporting DLS and with Dynamic Light Scattering set to on.