Microchip Capillary Electrophoresis for On-Line Monitoring of Inorganic Aerosols

A compact and affordable microchip-based system for the automated, in situ analysis of inorganic ions in atmospheric aerosols will be develop and verified against traditional, filter-based methods. Aerosol Dynamics, Inc., will combine two new technologies: (1) a growth tube impactor for particle collection, and (2) lab-on-a-chip (LOC) analysis of sulfates and nitrates. The growth tube impactor enlarges individual airborne particles by water condensation in a laminar, thermally diffusive flow. Once encapsulated within a water droplet, particles with a diameter of 0.015 µM or larger are deposited directly onto a small reservoir on the LOC. The LOC utilizes capillary electrophoresis with embedded conductivity detection. Separation of sulfates and nitrates is achieved in less than 2 minutes, with detection limits of 1 µM. The instrument will provide 5-minute time resolution for fine particulate matter (PM2.5) sulfate and nitrate, with detection limits of 100 ng/m3 or better. The analyzer will be both quiet and compact. The pressure drop required for sampling is just 0.5 kPa, and thus pumping requirements are small. As such, it will be suitable for microenvironmental sampling in offices, homes, schools, and air monitoring stations. By providing a low-cost alternative to other continuous analyzers, widespread deployment will be encouraged.