Absolute Mass and Size Measurement of Monodisperse Particles Using a Modified Millikan's Method: Part II—Application of Electro-Gravitational Aerosol Balance to Polystyrene Latex Particles of 100 nm to 1 μm in Average Diameter
The masses and diameters of monodisperse polystyrene latex particles ranging from 100 nm to 1 μ m in average diameter were determined using the electro-gravitational aerosol balance, a method that we proposed in a previous paper. Charged latex particles were introduced between parallel plate electrodes similar to a Millikan cell, and the particle survival rate after a certain holding time had elapsed was measured as a function of the applied voltage. The number average diameter and the corresponding particle mass were determined by fitting a theoretical survival rate spectrum to the experimentally observed spectrum using the least squares method. In this fitting, the value of the particle density obtained in a separate experiment was used. Detailed uncertainty analysis of the number average diameters thus determined was carried out. The expanded uncertainty with a coverage factor of 2, which corresponds approximately to a 95% confidence interval, was 0.66 nm, or 0.66%, for 100 nm particles and 1.8 nm, or 0.18%, for 1 μ m particles. The diameter values of 200 nm particles obtained under different operating conditions were found to agree within 0.3%. These results demonstrate that the present method is appropriate for use as the primary sizing method to develop particle size standards in the size range of 100 nm to 1 μ m.
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Document Type: Research Article
Affiliations: National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
Publication date: 2006-07-01