The goal of this project is to couple a compact tunable ultraviolet laser system with a jet-resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometer to provide a fieldable system for real-time concentration measurements of aromatic hazardous air pollutants (HAPs) in urban air environments. The jet-REMPI technique already has proven to be powerful for the measurement of HAPs at low detection limits (ppt) with high chemical specificity. However, this technique currently requires a complex and delicate laser source, which confines the instrument to the laboratory. By developing a truly portable device, measurements can be taken in the field with both high temporal and spatial resolution, data that are essential components of emissions modeling, dispersion modeling, source apportionment, and ultimately, human exposure modeling. This information cannot reliably be estimated or inferred by any current method, but must be acquired through actual field measurements under typical, time-varying ambient human exposure conditions. Despite the need for such data, reliable ambient concentrations have been measured for fewer than 40 percent of the 189 HAPs, which lends urgency to the development of a field jet-REMPI instrument to help fill gaps in the data. Phase I research will involve the design of a compact optical parametric oscillator laser specifically tailored for the jet-REMPI application and testing of the laser on the current mass spectrometer system at SRI International. Measurements with calibrated simulated air samples will be made for both neat compounds and mixtures of HAPs. The detection limits and chemical specificity performance of the system will be compared with the results already obtained at SRI. With performance validation, a design for a complete integrated jet-REMPI system for Phase II field tests will be generated. Supplemental
Keywords: small business, SBIR, organic air pollution, hazardous air pollutants, jet-resonance-enhanced multiphoton ionization, mass spectrometry, monitoring, real-time measurement
