For the Zetasizer Nano S or ZS instrument, the maximum concentration specification for size measurements is 40% w/v. This technical note contains details of the experimental procedures and results obtained from measurements of a nominally 100nm silica suspension at a concentration of 40%w/v as demonstration of this maximum concentration limit.
The 40% w/v silica suspension was placed into a DTS0012 disposable sizing cuvette with care being taken to ensure no air bubbles were present. The measurements were taken at 25°C.
The intensity size distributions obtained from 5 repeat measurements of a nominally 100nm silica suspension at a concentration of 40% w/v are shown in figure 1, demonstrating the repeatability of measurement at this concentration.
Figure 2 is an overplot of the correlation functions of these measurements, showing an excellent repeatability and an intercept of 0.77 indicating a good signal and a low probability of multiple scattering which would affect the size measured.
The results reported in this technical note confirm that the maximum concentration specification for size measurements on the Zetasizer Nano S or ZS is 40% w/v.