Grantee Research Project Results
Final Report: Trace-level Measurement of Complex Combustion Effluents and Residues using Multi-dimensional Gas Chromatography-Mass Spectrometry (MDGC-MS)
EPA Grant Number: R828190Title: Trace-level Measurement of Complex Combustion Effluents and Residues using Multi-dimensional Gas Chromatography-Mass Spectrometry (MDGC-MS)
Investigators: Rubey, Wayne A. , Taylor, Philip H. , Striebich, Richard
Institution: University of Dayton
EPA Project Officer: Hahn, Intaek
Project Period: June 1, 2000 through May 31, 2003
Project Amount: $335,000
RFA: Combustion Emissions (1999) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:
Our hypothesis was that organic emissions and organics extracted from particulate matter (PM) are more complex than standard gas chromatography-mass spectrometry (GC-MS)-based instrumentation currently can measure. This complexity affects quantitation for toxic compounds, thereby affecting risk assessments. There was a pressing need to better characterize these organic emissions from hazardous waste incinerators and PM extracts from various other combustion sources. The objective of this research project was to develop, test, and use advanced multidimensional GC-MS instrumentation to examine combustion effluents and residues.
In addition, there was a continuing need to conduct these experiments in a rapid fashion, without losing separation power in the chromatographic step. These rapid measurements were being dictated, to a degree, by a desire to conduct separations in a real-time or near-real-time fashion. Thus, a continuing objective for this research project was to develop the instrumentation with speed of analysis in mind.
Summary/Accomplishments (Outputs/Outcomes):
At the beginning of this research project, we used Multidimensional Gas Chromatography-Mass Spectrometry (MDGC-MS) for the analysis of several combustion mixtures. The mechanics of the analysis were to physically remove a section of an eluting solute zone in a high-resolution GC-MS experiment. This 10-20 second collection of chemical compounds was directed by gas flow to a cryogenic trap outside of the GC system, while the remainder of the experiment continued. After 30-50 minutes, the column was cooled, and the trap was heated to direct the fraction into another GC column (of different polarity), where the small fraction was separated more completely in a second 30-50 minute analysis. Detection in the secondary column was by mass spectrometry so that identifications of chemical components could be performed. This process was effective for component identification, but it took approximately 2 hours to identify compounds that represented only 10 seconds of a 50-minute analysis (1/300th) of the original analysis of the sample. Each 10-second sample also required one injection. It was our objective to conduct these analyses in a comprehensive fashion (i.e., to perform both the primary and secondary separation on each part of the sample for complete analysis with only one injection).
With complex combustion effluent analysis in mind, we set out building an analytical system, which would conduct the comprehensive (complete) analysis in a reasonable time. The design and construction of this first technique were essentially accomplished in the first 14-18 months of our research project, resulting in a working system capable of comprehensive (complete) analysis of entire mixtures using multidimensional GC-MS. The system constructed was described completely in journal publications, an MS thesis document, and unpublished conference presentations as described in the publications/presentations section below. Several samples were examined using MDGC-MS: (1) National Renewable Energy Laboratory (NREL) samples for diesel automobile exhaust; (2) samples obtained by the U.S. Environmental Protection Agency (EPA) combustion researchers (Dr. Brian Gullett) for analysis of endocrine disrupting chemicals; (3) combustion and precombustion samples provided by the U.S. Air Force (petroleum-derived jet fuels); and (4) samples from the U.S. Army (fog oil and fog oil combustion products). The important link between all of these samples is that they are all more complex than conventional GC-MS systems can analyze and that they are from, or are important in, combustion emissions.
Technically, this instrumentation is based on our experience with “heart-cutting”-the conventional technique of MDGC described above-where a portion of the primary column effluent is collected at the end of the column and directed to a trap outside of the GC itself before being reintroduced onto a second column. The only change in this procedure was that the trap for collecting the heartcut effluent from the primary column was now inside the GC, and actuated more quickly. With a faster secondary column, the analysis could keep up with the primary column programming so that the secondary analyses could be conducted continuously, while the primary column was still generating the first chromatogram.
Although this technique was very successful, it did not separate the complex components completely, and the run times were on the order of 3 hours or more. The final year of our research project was spent implementing new designs for heating and cooling of the secondary column using thermal gradient programmed gas chromatography, which would allow the analysis to be conducted by a factor of three faster. This technique is a technology developed and patented by W. Rubey, one of the co-Principal Investigators on this grant. By employing fast heating of the microbore GC columns contained in a negative thermal gradient, we examined fast secondary separations in a time period of 15 seconds. To optimize the conditions necessary to perform the fast analysis, we used a five-component model mixture, the components of which were selected because they had the same boiling point. This mixture was used to simulate the elution of a “heartcut” from the primary GC column in a MDGC configuration (i.e., the components eluting simultaneously from the primary nonpolar column would have the same vapor pressure. However, these five components were selected for their different molecular polarities (nonpolar to polar): alkane, alkene, single-ring aromatic, diaromatic, and oxygenate. This mixture was used to optimize the secondary separation and heating schemes.
With an optimized secondary separation, the primary and secondary separations were put together with the same cryotrap in between the two that was used during the first successful instrumentation development. The detector for all of these systems has been the Agilent (Hewlett Packard) benchtop mass spectrometer, which we realized some time ago was neither fast enough nor sensitive enough to perform this fast analysis. We evaluated other mass spectrometers available in our laboratory (specifically the Saturn ion-trap MS), but we found that these were not fast enough to keep up with the peaks being generated by this system. We conducted limited experiments with the existing MS system and limited the mass scanning range to increase scanning speed to realize the full benefit of the separation. Unfortunately, it was at this point that our time and money was expended for this grant.
We have pursued, with other internal funding, the acquisition of time of flight mass spectrometer (TOFMS). This mass spectrometer currently is being installed in our laboratory. We plan to install the TOFMS as the detector for the MDGC-MS system; it will provide the ultimate detector for this analysis technique of MDGC-TOFMS.
Although we were not able to complete the ultimate instrumentation under the time constraints of this grant, we have fulfilled almost every experiment originally proposed for this effort. In addition, we were able to identify new compounds in combustion samples, which have not yet been identified, due to the fact that: (1) they are not regulated (no one looks for them); (2) they are in low concentration; and (3) they are buried in a complex matrix that cannot be separated easily by conventional techniques. One such example occurred in the analysis of open burning of rural household wastes. We identified bisphenol A, a suspected endocrine disruptor in this mixture, which we could not see in conventional analyses. We worked with many government agencies to identify samples and components of samples, which may be important to their processes or the health effects related to their release into the environment. During this time, we directed the graduate work for two Masters of Science students, both of which have (or soon will have) completed their dissertations. We also have made every attempt to transfer MDGC technology to other researchers through conference presentations.
We think that the EPA program offices are very interested in our work under this grant, as they believe it has great potential in examining nontarget compounds in complex combustion mixtures. Our colleagues at EPA (Research Triangle Park) have provided several samples that have been used to provide direction as to what compounds might be present in complex combustion mixtures, but could not be observed by conventional techniques. This information is especially important in the area of endocrine disrupting chemicals; some of which may be produced in open burning of wastes.
Journal Articles:
No journal articles submitted with this report: View all 19 publications for this projectSupplemental Keywords:
multidimensional, risk assessments, endocrine disrupting chemicals, polycyclic aromatic hydrocarbon, PAH, oxygenated PAH, trace analysis, residues, preseparation, gas chromatography, GC, mass spectrometry, MS, gas chromatography-mass spectrometry, GC-MS, multidimensional gas chromatography-mass spectrometry, MDGC-MS, thermal gradient programmed gas chromatography, TGPGC, measurement methods, combustion effluents, residues, particulate matter, PM, analytical chemistry, complex combustion effluents, hazardous waste incinerators, organic emissions, products of incomplete combustion, PIC, qualitative identification of compounds., RFA, Scientific Discipline, Air, Waste, particulate matter, Environmental Chemistry, Chemistry, Incineration/Combustion, Engineering, Environmental Engineering, risk assessment, mass spectrometry, qualitative identification of compounds, products of incomplete combustion (PIC), hazardous waste incinerators, analytical chemistry, complex combustion effluents, multi-dimensional gas chromatographyProgress and Final Reports:
Original AbstractThe 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.