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. Our approach combines tow 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 diameter of 0.015 um 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 tell than tow minutes, with detection limits of 1 uM. The instrument will provide 5-min time resolution for PM2.5 sulfate and nitrate with detection limits of 1oo ng/m3 or better. The analyzer will be both quiet and compact. The pressure drop required for sampling is just 0.5kPa, and thus pumping requirements are small. As such, it will be suitable of microenvironmental sampling, in offices, homes and schools, as well as at air monitoring stations. By providing a low cost alternative to other continuous analyzers, widespread deployment will be encouraged