The ZAve size is calculated from a Cumulants analysis of the autocorrelation function measured by the instrument, and represents a single average size estimate.

The sizes generated by a non negative least squares analysis, which generates the size distribution graph, are reported as "Peak n Size", where "n" represents different peak numbers identified in the size distribution result.

Hello Vikas, the Z average size is not calculated from the intensity distribution. The instrument measures a correlation function (which describes the statistics of the scattering intensity fluctuations) and this function is then analyzed by two entirely different methods:

1. Cumulant fit: the autocorrelation function is fit to a single exponential decay function. [For this the logarithm of the correlation function is fit to a straight line versus linear delay time, and the slope is related to the mean diffusion coefficient and therefore size]

2. Regularization fit: here the autocorrelation function is mathematically "inverted" to find all the potential exponential decay functions that have may contributed to it. [Since this is a mathematically ill-posed problem, there is actually a range of solutions, and these can be narrowed down with certain assumptions, for example that no negative sizes exist, and that the solution should contain only relatively smooth peaks; with varying levels of smoothness in the general purpose or multiple narrow mode analysis]

Since these two fits are done entirely differently, there is no direct relation between one and the other. For monodisperse samples, the number should almost be the same, for polydisperse samples, the cumulant size will be close to the intensity weighted average of the peaks.

http://www.materials-talks.com/blog/2014/07/10/faq-peak-size-or-z-average-size-which-one-to-pick-in-dls/

It is very dangerous to replace in the process investigation the particles of two different sizes by particles of one average size. In a number of cases (electrophoresis, stimulated scattering, sedimentation, etc.) the rates of processes (charge transfer and the current, intensity and the frequency shift, sedimentation rate) are determined by the particles of only one size, often large, and remaining particles are not involved to the process or they are indirectly involved, for example, coagulating into larger particles. So I would advise not to move to the average size, and take into account both size fractions.

But if in intesity correlation function particles arise of radius of about 0.1 – 1 mm

But if the intensity distribution on the particle radii contains a peak of size 0.1 - 1 mm, this means that you see the artifact distribution peak, not associated with actual particle sizes, but arised from the time of their entry and exit from the scattering volume.