Abstract
In this study, the counting efficiencies of optical particle counters (OPC) were evaluated by using AIST-inkjet aerosol generator (AIST-IAG). Among the six particle size channels of an OPC (RION KC-31), the counting efficiencies were evaluated at two size channels (0.5 μm and 5.0 μm) which are used to monitor the cleanliness of the pharmaceutical manufacturing environments. Current industrial standards (ISO 21501-4 or JIS B 9921) define the particle sizes measured by an OPC as PSL-equivalent optical diameters, dPSL, while the particle diameters of IAG-generated particles are defined as volume equivalent diameter, dve. Therefore, we developed a method to experimentally find a dve-value whose dPSL-value measured by an OPC would fall within a desirable range. Particle generation rate of the AIST-IAG was fixed at 50 particles/s, and three types of water-soluble particles with different morphologies were generated: inorganic salt particles (NaCl) which were non-spherical, solid organic particles (lactose) which were near spherical, and a non-volatile liquid particle (ionic liquid). The measured counting efficiencies ranged from 1.000 to 1.005 and their expanded uncertainties ranged from 0.0052 to 0.0053. From these results it was concluded that AIST-IAG is an effective calibration device for precisely evaluating the counting efficiencies of OPC.
