Grantee Research Project Results
Final Report: Acrolein Monitor Using Quantum Cascade Laser Infrared Adsorption
EPA Contract Number: EPD06020Title: Acrolein Monitor Using Quantum Cascade Laser Infrared Adsorption
Investigators: Shorter, Joanne H
Small Business: Aerodyne Research Inc.
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2006 through August 31, 2006
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2006) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Endocrine Disruptors , Environmental Engineering , Particulate Matter , SBIR - Air and Climate , Small Business Innovation Research (SBIR) , Watersheds
Description:
Acrolein (CH2=CHCHO) is a toxic unsaturated aldehyde that has been identified in the U.S. Clean Air Act as a hazardous air pollutant (HAP). The objective of this Small Business Innovation Research (SBIR) project was to develop a fast response quantum cascade (QC) laser system based on the Tunable Infrared Laser Differential Absorption Spectroscopy method (TILDAS). The instrument was to be developed for high sensitivity and selectivity real-time measurement of acrolein, overcoming the limitations in both sensitivity and time response of present acrolein monitoring methods.
Improved measurement methods are needed to identify acrolein sources and to monitor its presence in ambient air. Current analytical methods for source monitoring (EPA Method 18 and CARB 430) and ambient monitoring (EPA Method TO-11A) rely on derivatization procedures and are not sufficient. In these standard methods, samples are collected on a solid sorbent cartridge coated with 2,4-dinitrophenylhydrazine (DNPH) or other suitable derivatization agent, followed by solvent desorption of the cartridge, and liquid injection of the eluent for high-performance liquid chromatography and UV-visible absorption analysis (Ho and Yu, 2002; Ho and Yu, 2004). Limitations of such methods include insufficient sensitivity, aldehyde loss on cartridges, and limited time response. The carbonyls also are unstable, both in underivatized form and in the DNPH derivative (Destaillats, et al., 2002; Liu, et al., 2001). More recently, other derivatization agents, including O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine, have been used to react with the carbonyls, including acrolein, to form thermastable derivatives that can be subsequently analyzed by thermal desorption and gas chromatography (GC)-mass spectroscopy (Destaillats, et al., 2002; Ho and Yu, 2002; Ho and Yu, 2004) or GC and electron capture detection (Tsai and Hee, 1999). All of these methods have time responses on the order of minutes or hours, require consumables that might be hazardous to handle, and have problems with sample loss. There also recently have been efforts to measure acrolein with a proton transfer reaction mass spectrometer instrument (Knighton, 2006). Improved technologies clearly are required to provide ambient monitoring of acrolein.
The improved acrolein monitor will obtain sensitivities in the parts-per-billion (ppb) range for source monitoring and parts-per-trillion (ppt) range for ambient conditions. Both requirements are achievable with the QC laser-based instrument. The instrument will share elements of previously designed Aerodyne Research, Inc. (ARI) instruments and some unique aspects required for monitoring acrolein. The instrument will be a fully integrated electro-optical system, easy to operate, and capable of providing real-time measurements with high-time resolution (better than 1 second). The instrument will not require calibration gases because the retrieved concentration of acrolein will be based on fitting the absorbance spectra to the calibrated line strengths and path length of the instrument.
Summary/Accomplishments (Outputs/Outcomes):
In the Phase I project, we have conducted specific tasks to demonstrate the feasibility of a QC-TILDAS instrument for acrolein monitoring in both ambient air and from sources. We have investigated the infrared spectra of acrolein to assess the optimum wavelengths and absorption linestrengths for its detection. Through spectral simulations and laboratory measurements, we determined that the 958 cm-1 region was the preferred region for acrolein monitoring.
Various possible scrubbers were tested to select one that can provide acrolein-free background air without removing other components or otherwise perturbing the measurement system. Such background air is necessary to remove interference from the analysis spectrum by using background correction methods. DNPH cartridges and sorption tubes were tested but found unacceptable. However, room temperature chemical scrubbers composed of Sofnocat (Molecular Products), with highly active precious metal catalysts or Chemsorb 1505 (C*Chem), an impregnated carbon, both removed acrolein to below the detection limit without significantly disturbing other known components in the air samples. Both scrubbers were found to be acceptable for incorporation into a QC-TILDAS acrolein monitor for the background correction method.
Monitoring of acrolein emission sources and in ambient air was conducted. Long-term monitoring of acrolein in the ambient air sampled from the roof of ARI demonstrated the feasibility of obtaining a sensitivity of 1.16 ppbv Hz-1/2. Using an Allan plot analysis of long-term data, we obtained a variance equal to 0.28 ppbv after 100 seconds of measurement time (i.e., 50 seconds of sample and 50 seconds of background). Emissions of acrolein from combustion sources including burning wood, vehicle exhaust, and cigarette smoke were successfully monitored. In these samples the most significant interference is ethylene, particularly in vehicle exhaust. The laboratory studies demonstrated the excellent effectiveness of background subtraction techniques with selective removal of acrolein to improve the sensitivity of the QC-TILDAS system to acrolein in the presence of high levels of ethylene. A preliminary design for the Phase II acrolein monitor includes a set of modules combined into a fieldable unit.
Conclusions:
We have successfully completed all of the tasks of the Phase I project and have shown the feasibility of a sensitive, fast-response QC laser system for monitoring acrolein. In Phase I, we successfully demonstrated sensitivity to acrolein of 1.2 ppbv in 1 second and 0.28 ppbv in 100 seconds. A room temperature scrubber for background suppression has been identified. We have demonstrated the feasibility of sensitively detecting acrolein in a complex combustion matrix, including vehicle exhaust, burning wood, and cigarette smoke.
References:
Destaillats H, Spaulding RS, and Charles MJ. Ambient air measurement of acrolein and other carbonyls at the Oakland-San Francisco Bay Bridge toll plaza. Environmental Science & Technology 2002;36(10):2227-2235.
U.S. Environmental Protection Agency, Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air, Method TO-11A, Center for Environmental Research Information, Office of Research and Development, EPA, Cincinnati, OH, 1999.
Ho SS, Yu JZ. Feasibility of collection and analysis of airborne carbonyls by on-sorbent derivatization and thermal desorption. Analytical Chemistry 2002;74(6):1232-1240.
Ho SS, Yu JZ. Determination of airborne carbonyls: comparison of a thermal desorption/GC method with the standard DNPH/HPLC method. Environmental Science & Technology 2004;38(3):862-870.
Knighton B. Personal communication, Montana State University, 2006.
Liu LJS, Dills RL, Paulsen M, Kalman DA. Evaluation of media and derivatization chemistry for six aldehydes in a passive sampler. Environmental Science & Technology 2001;35(11):2301-2308.
Tsai SW, Hee SS. A new passive sampler for regulated workplace aldehydes. Applied Occupational and Environmental Hygiene 1999;14(4):255-262.
There exists a need for commercially available air quality instrumentation for acrolein and other toxic air pollutants for routine air quality monitoring in urban areas for health effect assessment, and at industrial sites for measuring direct emissions of these gases from manufacturing facilities. Acrolein is produced by combustion in internal combustion engines, vehicle exhaust, aircraft emissions, as a by-product of petroleum refining, and during industrial processing of wood and paper products. The diversity of sources and the relatively high reactivity of acrolein require a highly sensitive, easily portable, and fast response measurement technique. The infrared laser detection technique has wide commercial applications both for routine air quality monitoring and for source assessment of hazardous air pollutants.
Supplemental Keywords:
air quality monitoring, emission detection, acrolein, quantum cascade laser spectrometer, small business, SBIR, hazardous air pollutant, HAP, air emissions, air pollution, monitoring, analytical, environmental measurement techniques, spectroscopy, Tunable Infrared Laser Differential Adsorption Spectroscopy, TILDAS, EPA,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Environmental Chemistry, Monitoring/Modeling, Environmental Monitoring, Environmental Engineering, acrolein monitoring, emissions monitoring, HAPS, air pollution, quantum cascade laser infrared adsorption, air quality assessments, aerosol analyzers, air quality, atmospheric chemistrySBIR Phase II:
Acrolein Monitor Using Quantum Cascade Laser Infrared Absorption | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.