Final Report: Microchip Capillary Electrophoresis for Online Measurement of Inorganic Aerosols

EPA Contract Number: EPD05058
Title: Microchip Capillary Electrophoresis for Online Measurement of Inorganic Aerosols
Investigators: Hering, Susanne
Small Business: Aerosol Dynamics Inc.
EPA Contact: Manager, SBIR Program
Phase: II
Project Period: April 4, 2005 through June 30, 2006
Project Amount: $219,136
RFA: Small Business Innovation Research (SBIR) - Phase II (2005) Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , SBIR - Air Pollution , Small Business Innovation Research (SBIR)


The objective of this research project was to develop a methodology for online analysis of particulate sulfates, nitrates, and other inorganic ions in a compact and inexpensive instrument through the application of emerging “laboratory-on-a-chip” (LOC) techniques.

Aerosol Dynamics Inc., developed a new instrument, the Aerosol Capillary Electrophoresis (ACE), which combines two new technologies: a “growth tube” impactor technique for the deposition of fine and ultrafine aerosol onto a solid surface at low-pressure drop and emerging microchip analytical methodologies. The growth tube enlarges ambient particles by water vapor condensation in a laminar, thermally diffusive flow analogous to what happens within the human lung on a cold day. Once enlarged, the particles are deposited readily by impaction into a sample reservoir on an analytical microchip. The aerosol sample is analyzed by capillary electrophoresis (CE) coupled with an embedded conductivity detector. An internal standard provides quantification of the deposited mass, from which the ambient concentrations are derived. The system is small and its components are inexpensive.

Summary/Accomplishments (Outputs/Outcomes):

The growth tube technology was adapted to provide direct collection on the analytical microchip, yielding concentrated deposits of fine and ultrafine ambient particles. With this technique, particles are collected with high efficiency, but low-pressure drop. A new type of analytical microchip was developed that effectively dampens the hydrodynamic noise from the collector, eliminating interference from the aerosol collection, allowing direct collection to proceed during the chemical analysis. Analyses are done by on-chip CE, with direct conductivity detection. The microchip provides 3-sigma detection limits below 1 μM for both sulfate and nitrate, with separation times of just under 2 minutes. The prototype instrument provides 5-minute time resolution for a suite of PM2.5 ions, with detection limits of 1 μg/m3. Further refinement of the system is needed, however, to optimize the long-term performance and reliability. Expected fabrication costs are below $5,000.

Specific accomplishments of this project include: (1) developed a growth tube collector capable of depositing particles as small as 15 nm within 5-mm diameter reservoir at pressure drops of less than 1 inch of water; (2) designed, fabricated, and tested a new lab-on-a-chip with an integrated interface that accommodates the growth tube collector without interference to the analysis; (3) developed a chip-based analytical method for the clear separation of sulfate, nitrate, and chloride; (4) incorporated an internal standard to allow quantification of these anions; (5) demonstrated by comparison to ion chromatography analysis that the collection method is comparable to standard techniques; and (6) operated the integrated system on ambient aerosol successfully.


With this project, Aerosol Dynamics Inc., successfully made the crucial steps from the original concept to the development of the critical aspects of the ACE system. Prior to commercialization, further prototype development will be pursued to allow automatic flushing of the sample reservoir and to prolong the life of unattended operation. Improved packaging will aid in the robustness of the design. Additional field testing, using side-by-side monitoring with filter-based and ion chromatography-based systems, will be needed before commercialization.

Importantly, the size of the system and its expected cost meet the original target goals of Aerosol Dynamics Inc. Although no effort has been made to provide a compact system at this stage, the size of the complete ACE system is approximately one-tenth the size of the automated ion chromatography systems now available. With an appropriately designed conductivity detector and power supply, the size of the system will be smaller and less expensive than any automated aerosol system introduced to date.

Applications include routine measurements at air quality monitoring stations, microenvironmental monitoring to support epidemiological studies, and intensive monitoring to establish spatial and temporal variability. The system also is well suited for operation on aircraft monitoring platforms, where space and power can be at a premium.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other project views: All 3 publications 1 publications in selected types All 1 journal articles
Type Citation Project Document Sources
Journal Article Liu Y, MacDonald DA, Yu XY, Hering SV, Collett JL, Henry CS. Analysis of anions in ambient aerosols by microchip capillary electrophoresis. Analyst 2006;131(11):1226-1231. EPD05058 (Final)
  • Abstract from PubMed
  • Supplemental Keywords:

    small business, SBIR, microchip capillary electrophoresis, inorganic aerosols, growth tube impactor, lab-on-a-chip, LOC, particulate matter, PM2.5, online measurement, speciation monitoring, aerosol analyzers, microchip capillary electrophoresis,, RFA, Scientific Discipline, PHYSICAL ASPECTS, Air, Ecosystem Protection/Environmental Exposure & Risk, RESEARCH, particulate matter, Air Quality, Environmental Chemistry, Monitoring/Modeling, Analytical Chemistry, Monitoring, Environmental Monitoring, Atmospheric Sciences, State of Matter, Engineering, Chemistry, & Physics, ambient aerosol, atmospheric measurements, inorganic aerosols, chemical characteristics, human health effects, air quality models, monitoring stations, emissions measurement, modeling, gas chromatography, air sampling, air quality model, microchip capillary electrophoresis, human exposure, atmospheric aerosols, particulate matter mass, PM2.5, continuous emissions monitoring, aerosol, modeling studies, capillary electrophoresis, air quality field measurements, aerosol analyzers, atmospheric chemistry, chemical speciation sampling

    SBIR Phase I:

    Microchip Capillary Electrophoresis for Online Measurement of Inorganic Aerosols  | Final Report