For the Zetasizer Nano Z, ZS or ZS90 instrument, the maximum concentration specification for zeta potential measurements is 40% w/v.
This technical note contains details of the experimental procedures and results obtained from measurements of a 40% polyurethane dispersion as demonstration of this maximum concentration specification for zeta potential measurements.
Various concentrations of the polyurethane dispersion were prepared in 5% v/v triethylamine (to maintain ionic strength). All samples were measured on a Zetasizer Nano ZS at 25oC using the high concentration zeta potential cell ZEN1010. A field of 40V was applied across the electrode spacing of 16mm (field strength of 25V/cm).
Figure 1 shows a plot of zeta potential as a function of concentration for an aqueous polyurethane dispersion with the addition of 5% triethylamine. The concentration dependence seen in the zeta potential results is discussed in reference 1.
Figure 2 shows the phase plots obtained from a 40% w/v polyurethane dispersion. These results demonstrate the ability of the Zetasizer Nano to measure samples up to 40%w/v concentration.
The results reported in this technical note confirm that the maximum concentration capability for zeta potential measurements with the Zetasizer Nano Z, ZS or ZS90 is 40% w/v.
 M. Kaszuba, J. Corbett, F.M Watson and A. Jones (2010) Phil. Trans. R. Soc. A368, 4439-4451.