Mass–Mobility Measurements Using a Centrifugal Particle Mass Analyzer and Differential Mobility Spectrometer

Abstract

Mass–mobility measurements using a centrifugal particle mass analyzer (CPMA) and differential mobility spectrometer (DMS) are demonstrated. The CPMA, which classifies an aerosol by mass-to-charge ratio, is used upstream of a DMS, which measures the mobility size distribution of the mass-classified particles in real-time. This system allows for mass–mobility measurements to be made on transient sources at one particle mass or an entire effective density distribution for steady state sources in minutes. Since the CPMA classifies particles by mass-to-charge ratio and multiply charged particles are present, particles of several different masses will be measured by the DMS. Therefore, a correction scheme is required to make accurate measurements. To validate this measurement scheme, two different CPMA-DMS systems were used to measure the known density of di(2ethylhexyl) sebacate (DEHS). The first system consisted of a CPMA and standard DMS500 (Cambustion). This system measured an average effective density of 1027 kg/m3 or within 12.6% of the accepted value with an estimated uncertainty of 30.1% (with 95% confidence). The second system consisted of a CPMA and modified DMS. The modified DMS was a DMS500 with the corona charger disabled and sample and sheath flow rates lowered, decreasing the uncertainty in the mobility measurement. This system measured an average effective density of 964 kg/m3 or within 5.7% of the accepted value with an uncertainty of 9.5–10.4% depending on particle mobility size. Finally, it was determined that multiple-charge correction and size calibration were required, with each correction causing a maximum change in measured effective density greater than 10%. Copyright 2013 American Association for Aerosol Research