Single Particle Laser Ablation Time of Flight Mass Spectrometer: Density Measurements and Detection of Coated Polystyrene Latex (PSL) Particles
Abstract Single Particle Laser Ablation Time of flight Mass Spectrometer (SPLAT-MS) was designed to characterize aerosol particles individually. It can measure particle composition, size, and density simultaneously in real time. In this experiment, we use DMA to select mobility diameter of particles, and use SPLAT to measure vacuum aerodynamic diameter. Particle density was derived from the vacuum aerodynamic and mobility diameters. In a high precision approach, an internal calibrant was used to increase measurement accuracy, which is suitable for laboratory studies to monitor slight changes in particle density.
Quantitative measurements are always an issue when using laser ablation mass spectrometry, especially in the presence of alkali metals. We studied coated polystyrene latex particles by Na-containing chemicals, in which we measure with nanometer resolution individual particle mobility diameter, vacuum aerodynamic diameter and mass spectrum using SPLAT. Vacuum aerodynamic diameters or densities are used to separate coated particles from pure coating chemical particles. We find that the coating chemicals have significant influence to the detection of PSL core. The intensity decrease of PSL signals is not due to the weak laser ablation but a consequence of ion suppression from charge transfer processes.