High-Throughput, Robotic System for Analysis of Aerosol Sampling Filters

air pollution from transportation
Opportunity

Available for Licensing
TRL: 5

IP Status

US Utility Patent Pending (Not Yet Published)

Inventors

​Christian L’Orange
John Volckens
Gabriel Neymark
Ellison Carter

At A Glance

Researchers at Colorado State University have developed an automated filter analysis system for high-throughput gravimetric mass and optical black carbon measurements of filter-based aerosol samples. The Automated Air Analysis Facility (AIRLIFT) system (1) increases sample throughput, (2) achieves good analytic figures of merit (bias, precision, and limit of detection), (3) reduces personnel burden, and (4) serves as a platform for multiplexed analysis of air sampling filters. Furthermore, the AIRLIFT system is compliant with US EPA gravimetric filter analysis requirements.

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Reference No.: 2021-048

Background

Exposure to airborne particulate matter (PM) is the leading environmental risk factor for premature disease and death on the planet. The gold-standard method for determination of PM mass concentrations is gravimetric analysis of air sampling filters. The United States Environmental Protection Agency (US EPA) describes gravimetric analysis as the sole Federal Reference Method for the determination of PM2.5 and PM10 concentrations (particles with aerodynamic diameters ≤ 2.5 um and 10 µm, respectively) in air; this method is then used to establish equivalence for all other methods (e.g., light-scattering, beta-attenuation). Unfortunately, gravimetric filter analysis is tedious and prone to bias/imprecision unless strict quality control procedures are employed.

Gravimetric analysis requires quantifying the mass of PM accumulated on an air sampling filter (i.e., weighing the filter on an analytic microbalance before and after a timed air sample is collected at a pre-determined flow rate). Precise measurements are needed because the differential mass (of accumulated PM) is often small compared to the total filter mass. Static electricity and slight variations in environmental conditions can bias the measurement. Regulatory agencies such as the US EPA, among others, have established requirements for gravimetric analysis. Slight differences in procedures and guidelines exist between different regulatory agencies; however, many published procedures include similar approaches and performance limits, such as control of ambient temperature and humidity, electrostatic discharge of the filter prior to weighing, and rules for filter handling and equilibration.

The challenge of making precise and unbiased gravimetric filter measurements is compounded by the tedious, labor-intensive nature of the measurement. Human errors are common and include failure to maintain steady and appropriate environmental conditions, failure to wait until the balance has stabilized before recording a reading, and transcription mistakes (when manually recording readings). The repetitive nature of filter weighing is monotonous; thus, the likelihood of human error increases with sample size as individuals tend to rush the weighing process or become negligent to proper filter handling procedures. The weighing of filters is also time intensive. Each replicate measurement of a gravimetric filter can take several minutes. A trained technician, following EPA protocol, can manually weigh only 10-15 filters per hour.

Benefits
  • Automation of optical Black carbon analysis
  • Can greatly increase filter analysis throughput
  • Meets or exceeds US EPA requirements for filter weighing
  • Ability to configure system to include additional spectroscopic analyses
  • Additional quality assurance capabilities that include incorporation of photos/videos
  • Achieves the levels or measurement repeatability necessary for air quality related studies
  • Reduces tedious time-consuming process of manually weighing filters by a factor ~4
  • Capable of analyzing approximately 260 filters per day
Applications
  • Air Quality Monitoring
  • Direct application for organizations who work directly or indirectly with aerosol related air quality

Last updated: August 2021

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