Surfactant-free latex spheres for size calibration of mobility particle sizers in atmospheric aerosol applications

Scanning mobility particle sizers (SMPS) are common instruments in laboratory and field aerosol studies. They are, however, complex instruments whose accuracy depends in part on reproducible size calibration. The commonly recommended calibration procedure uses polystyrene latex spheres in a solution with surfactant added to minimize coagulation of the particles. The surfactant can contribute significantly to the overall particle number size distribution and in some cases overlap the peak due to the latex spheres. We describe here the application of surfactant-free latex spheres which to the best of our knowledge have not been used in atmospheric applications before but which have significant advantages, including ease of use and cost.