Evaluation of concentration measurement techniques of colloidal nanoparticles for microfiltration and ultrafiltration applications: Inductively coupled plasma-mass spectrometry, nanoparticle tracking analysis and electrospray-scanning mobility particle sizer

Three different liquid-borne particle concentration measurement methods, including the inductively coupled plasma-mass spectrometry (ICP-MS), nanoparticle tracking analysis (NTA) and electrospray-scanning mobility particle sizer (ES-SMPS), for determining the efficiency of liquid filtration were investigated and compared for their applicability and feasibility. These methods were first calibrated using commercial Au monospheres with various sizes from 5 to 50 nm and several sizes of NIST traceable polystyrene latex (PSL) from 20 to 125 nm. Calibration results showed that the prepared concentrations of liquid-borne particles according to that provided by the manufacturers were proportional to the concentrations measured by all these methods. The calibration results were then used to determine the filtration efficiencies of Au and PSL nanoparticles through the 0.1 μm pore diameter polycarbonate track-etched (PCTE or Nuclepore filter) membrane filters, which were performed as the dead-end type filtration. It was found that the filtration efficiencies obtained by different measurement methods under the same condition were comparable with each other. The results of this study provide a very useful guidance in selecting the proper method for liquid-borne particle filtrations under different circumstances.