Particle Sizing and Zeta Potential of Silica Koestrosol (Basis for Certified Reference Material ERM-FD100 for Nanoparticles) by Acoustics and Electroacoustics

Precipitated silica Koestrosol 1530 is the basis for the recently adopted certified reference material ERM-FD100 used for nanotechnology. A similar reference material based on another precipitated silica (silica Ludox(TM)) has been used for testing ultrasound based instruments for particle sizing and zeta potential in concentrated dispersions and emulsions for the past two decades. In this study we test silica Koestrosol as a potential replacement for the silica Ludox(TM) since the latter has not been certified. The measurements were performed using ultrasound based instruments, which were suitable for concentrated systems. Two laboratories (USA and Germany) with 3 different instruments were involved, measuring samples at 5?% mass fraction. Samples mass fraction was 5?%. The statistically averaged mass-based median particle size was found to be 22.4?+/-?0.5 nm, which is within range of certified values obtained for more diluted samples. Values for ?-potential were measured as 26.7?+/-?0.9?mV, with precision that is order of magnitude better then reported before.