AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Development of a Microfluidic Instrument for the Real-time Measurement of Aerosol Oxidative Potential Using DTT (Dithiothreitol) Assay
TING FANG, Vishal Verma, Rodney Weber, Georgia Institute of Technology
Abstract Number: 121 Working Group: Linking Aerosols with Public Health in a Changing World
Abstract The aerosol oxidative potential has gained increasing importance due to its possible relevance to adverse health effects of ambient particles (PM). One of the most widely used measures of oxidative potential of particles is the DTT (Dithiothreitol) assay. This assay monitors the consumption rate of DTT as catalyzed by the redox-active species in PM. The major concern with the assay is the substantial PM concentration, required to yield a detectable signal. While filter-based collection approaches with long sampling duration are commonly used, they could entail artifacts due to losses of DTT-active semi-volatile species during sampling and handling procedures. Besides, composite samples collected over a long period of time cannot capture short time scale variations in the aerosol oxidative potential that could provide unique insights on sources and atmospheric processes affecting DTT activity. Based on the flow injection analysis (FIA) technique, we aim to adapt the DTT assay to an online system coupled to a particles-into-liquid sampler (PILS) for continuous real-time measurement of aerosol oxidative potential. In this approach, PM2.5 ambient particles are directly collected into Deionized water via PILS at an air-flow of 16.7 L/min and carrier DI water flow of 0.1 mL/min. The aqueous sample, after filtering through a PTFE syringe filter (pore size = 0.45 micro-meter), is injected into a flowing carrier stream containing DTT. Varies reagents are mixed by generating a turbulent flow using super serpentine reactors (Global FIA). The consumption rate of DTT is monitored using a Liquid Wave-guide Capillary Cell (LWCC-3250; World Precision Instruments, Inc., Florida) with optical path length of 2.5 m, coupled to an online spectrophotometer (Ocean Optics, Inc., Dunedin, Florida, USA), which included a UV-VIS light source (Ocean Optics DT-Mini-2), multi-wavelength light detector (USB4000 Miniature Fiber Optic Spectrometer), and a data acquisition software (SpectraSuite). The performance of this online DTT system and field application will be discussed.