The Role of Process Analytical Chemistry in Pollution Prevention

Chapter 4

The Role of Process Analytical Chemistry in Pollution Prevention Elizabeth A. McGrath, Deborah L. Illman, and Bruce R. Kowalski

Downloaded by UNIV LAVAL on May 14, 2016 | http://pubs.acs.org Publication Date: October 6, 1992 | doi: 10.1021/bk-1992-0508.ch004

Center for Process Analytical Chemistry, University of Washington, BG-10, Seattle, WA 98195

The Center for Process Analytical Chemistry (CPAC) was launched in 1984 as a partnership with the chemical and materials industry to address fundamental research questions at the frontier of process analysis. In collaboration with 46 corporate sponsors and 4 national laboratories, C P A C is developing new sensors and analyzers, integrated with chemometrics methods, to enhance process control. In addition to improving product quality and process efficiency, advances in this field will lead to improved process safety and accountability. By obtaining better chemical information about the process, it will be possible to achieve tighter process control, preventing process upsets and release of pollutants, and ultimately, to improve the design of new chemical plants in terms of safety and reliability. Programs at the Center focus on four aspects of process analytical chemistry for pollution prevention: (1) new sensors, such as optical waveguides for in situ, remote, automated and/or continuous environmental monitoring; (2) instrumentation coupled with chemometrics for tighter process control; (3) sensing methods for recycling (such as a remote technique for plastics identification); and (4) new graduate curriculum, team-taught by C P A C sponsors, with case studies from actual industrial processes. The Center for Process Analytical Chemistry (CPAC) was first proposed by Bruce Kowalski and colleagues at the University of Washington in 1982. The original vision was a Center that could provide a common ground for scientists and engineers from academia and industry to pursue areas of interest and need in continuous chemical monitoring, remote sensing, and crisis alerting systems. "The initial idea behind the concept of process analytical chemistry came when Professor Kowalski matched these needs and interests with the possibility of using chemometrics to enable analytical instruments to monitor a chemical process, on-line, as an integral part of the process" (J). At this time, Dr. James Callis, now Co-Director of

0097-6156/92/0508-0033$06.00/0 © 1992 American Chemical Society

Breen and Dellarco; Pollution Prevention in Industrial Processes ACS Symposium Series; American Chemical Society: Washington, DC, 1992.


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C P A C , was asked to participate in the creation of the Center by contributing his expertise in the area of instrument development. The development of in-line and noninvasive analytical instrumentation for process control and optimization, intelligent analytical instrumentation, remote sensing and continuous chemical monitoring was the specific focus of the Center. Since the industrial environment presents a number of challenging problems (e.g., noise, vibration, temperature extremes, challenging sample conditions, etc.), new sensors needed to be rugged, reliable, inexpensive, with fast-response, and incorporating automated calibration, error detection and correction features (2). They must also be able to detect the analyte of interest in the presence of interference and matrix effects and provide information that is relevant and useful to process control. Therefore, a concomitant purpose of the Center was the development of "the potential of multivariate data analysis and pattern recognition techniques to enhance instrument calibration, resolution, sensitivity and for data interpretation and feedback... for on-line and continuous monitoring systems" (1). Because manufacturing operations are not easily modeled, statistical methods that empirically determine correlations between process parameters and product performance are essential for feedback control. In 1984, C P A C became a reality as a partnership between the University of Washington, the National Science Foundation, and 21 founding industrial sponsors. Researchers at C P A C are developing new sensing technologies for use as an integral part of chemical systems, including in-line sensors, rapid separation techniques, chemometrics, and methods for nondestructive spectral determinations (i). This approach is designed to move chemical sensing away from the off-line/at-line measurements and toward the ultimate goal of in-line and noninvasive methods that can be utilized in real-time feedback control of chemical processes. Riebe and Eustace (3) have characterized process analytical chemistry (PAC) as a subdiscipline of analytical chemistry that, unlike traditional analytical chemistry, is performed on the "front lines" of the chemical process industry. The philosophy of PAC is quite different from traditional analytical chemistry, which is performed in sophisticated laboratories by highly trained specialists. The first and most obvious difference is location of the analysis (3). While a traditional analytical lab is centralized, P A C analyzers are located right with the process. Delay time associated with transporting, bookkeeping and analysis of samples is reduced or eliminated. Second, this reduction in the time frame for obtaining results is another benefit of PAC; here results are used to adjust the process not identify products that must be scrapped or reworked (3). Production schedules are shortened since P A C data can be used immediately for process control and optimization. Lastly, by its nature the process analytical world demands generalists and problem solvers. Unlike traditional analytical chemistry, PAC requires a team approach since it is problem-driven, not technique-driven (3). Only through the close interaction of process chemical engineers, process and analytical chemists and instrument and electronics engineers and technicians can this goal be achieved (4)For discussion, PAC may be divided into 5 eras: off-line, at-line, on-line, in-line and noninvasive (5). These eras describe a progression from traditional analysis



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Process Analytical Chemistry in Pollution Prevention

toward the ultimate goals of process analytical chemistry, in-line or noninvasive monitoring. Both the off-line and at-line eras require the manual removal and transport of the sample to the measuring instrument. Off-line samples are analyzed in a centralized facility where the benefits of time-shared equipment may be outweighed by delays in obtaining results, additional administrative costs, and competition among users for the resources. At-line analysis employs a dedicated instrument, which may be simpler since it has limited applications, located in close proximity to the process. These two processes are closer in nature to traditional analytical chemical analysis. The distinction between traditional and process analytical chemistry begins to widen with the on-line era. Here an automated sampling system extracts, conditions, and presents the sample to an analytical instrument for analysis. Online analysis may be divided into two categories: intermittent, which requires injection of a portion of the sample stream into the instrument, and continuous, which allows the sample to flow continuously through the instrument. The in-line methods eliminate the need to construct a separate analytical line to properly sample the main stream and present it to the instrument at a suitable temperature and pressure. Using the appropriate chemical probe, analysis is performed in situ within the process line. These probes may be chemically specific or composed of a sensor array, a set of semi-selective sensors, each of which has a different response profile to the analytes of interest. The fifth era, noninvasive, may represent the ultimate goal of P A C . By eliminating a physical probe it is also possible to eliminate sampling problems associated with sensor fouling or sample contamination. This technology has great potential for use in the pharmaceutical and biotechnology industry. Process analytical chemistry (PAC) is a new paradigm for chemical analysis. P A C involves both fundamental research and applications development, in order to produce information with the degree of chemical specificity, limits of detection, and rejection of interferences, necessary for meaningful analytical results. Advances in this field are important to the continued competitiveness of American industry, which depends on such factors as process optimization and control, energy efficiency, and automation (3). In the chemical industry, it is generally recognized that the greatest returns on investments in manufacturing or processing plants are obtained from investments in process control. It has been claimed that profits could be greatly increased by reducing 'quality costs'—the dollars lost when a product fails to meet specifications because the process could not be adequately controlled (3). In a recent survey conducted by the United States National Institute of Standards and Technology (NIST), the respondents knew of no existing sensors, instruments or methods to address about 25% of the described measurement problems (6). The primary benefit of PAC, a reduction in quality costs, results from streamlining manufacturing process efficiency and subsequently, improving product quality. Another important benefit is an increase in worker safety, also resulting from the better understanding, hence, control of these processes (7, 8). But there is an additional benefit, that is becoming more important as time goes on. Process analytical chemistry will play an increasing role in environmental protection. By improving manufacturing efficiency, there is a reduction of resources lost to


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the waste stream. Employing the technological and methodological advances in P A C , it is possible for industries to simultaneously minimize plant effluent release and improve product quality (5). Therefore, the environmental perspective is no longer fear of out-of-compliance operation, but knowledge that waste and byproducts are minimized or possibly eliminated by a process that is running within acceptable boundaries (3). The United States Environmental Protection Agency (EPA) now realizes that "end-of-the-pipe" regulations are ineffective in dealing with today's environmental discharges (9, 10). The E P A , established as the primary Federal agency responsible for implementing the nation's environmental laws, has seen its mission largely as managing the reduction of pollution, particularly that pollution defined in the laws that it administers. As a result, past U.S. environmental policy has been fragmentary and reactive rather than proactive. A report titled, "Reducing Risks," prepared by the EPA Science Advisory Board, recommends that U.S. environmental policy must "evolve to become more integrated and focused on opportunities for environmental improvement" (10). Because this country and the rest of the world are facing burgeoning environmental problems resulting from unprecedented population growth and worldwide industrial expansion, past practices of controlling the "end-of-the-pipe" where pollutants enter the environment are not sufficient. In addition, it has become apparent that the task of remediating the damage to the environment "after-the-fact" is too difficult and expensive for the government and industries involved. Once generated, the cost of cleaning up and disposing of pollutants can be enormous, as exemplified by the Superfund program, Department of Energy's cleanup of nuclear sites (11, 12), and cancellation and disposal of chemicals already in use. End-of-pipe controls and waste disposal should be the last line of environmental defense. Of primary concern should be preventing pollution at the front end, by ensuring that the processes run under tight control, by substituting less hazardous chemicals, and by recycling by-products or redesigning production processes. One obvious solution is a "front-end" reduction in pollutants in the waste stream. The diligent application of P A C can help reduce or prevent the release of pollutants. By obtaining better chemical information about the process, it will be possible to achieve tighter control and to prevent process upsets and release of pollutants. Unlike end-of-pipe controls, front-end control eliminates the transfer of pollutants from one media to another because pollutants are not generated in the first place (9). Businesses can gain economic benefits by saving resources and avoiding the costs and liabilities associated with waste disposal and cleanup. Therefore, the ultimate in environmental protection is pollution prevention— eliminating problems before they occur. In this regard, P A C represents a major adjunct to the other facets of environmental analytical chemistry. In addition, pollution prevention might also encompass the management of existing contaminated sites, e.g., "superfund" and government nuclear facilities. There is a need for new methods of monitoring the environment that can provide information on the location and movement of existing contaminants. Ecosystems are also chemical processes for which in-line, real-time analytical capabilities are



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Process Analytical Chemistry in Pollution Prevention

desired (3). A recent Congressional Office of Technology Assessment (OTA) document finds that clean-up efforts at D O E nuclear production sites have been "hampered by lack of ready technical solutions, reliable data and qualified personnel... (4)." New sensors and instruments for in situ, remote, automated, and/or continuous analysis with built-in calibration, error detection, and correction must be developed to operate in complex environmental matrices. To be effective, these sensors will need many of the qualities (e.g., rugged, reliable, self-calibrating, etc.) necessary for sensors being developed for use in industrial chemical processes. These new technologies will enable the surveillance of underground contaminant plumes and provide post-closure verification of the success of remediation efforts. They will also provide an "early warning" of potential contamination of nonpolluted soil and groundwater. These monitoring systems will need to be able to work in some very challenging settings (e.g., remote areas, down wells, radioactive matrices) and much of this technology has yet to be developed. Underway at C P A C is a major environmental initiative to conduct fundamental research on new sensing technologies with respect to the two main thrusts described above. As we look to the future, the needs are compelling. The time has come for government and industry to join forces and create "kinder" industrial practices that protect the environment and make good economic sense (13). To quote EPA's Administrator William Reilly, "...let anyone who doubts the wisdom of pollution control—or who believes there is a conflict between economic growth and environmental protection—let them go to Eastern Europe. Policies in Communist Europe designed to stimulate economic development by foregoing pollution controls ended by wrecking the economy and also ravaging the environment" (9). Pollution prevention has become the slogan for all EPA programs (9, 13, 14). Among the ten recommendations for establishing the direction of federal environmental policy in the future, the Scientific Advisory Board (SAB) stresses "...EPA should emphasize pollution prevention as the preferred option for reducing risk" (10). Armed with the results of the SAB report, Administrator Reilly has placed pollution prevention high on his strategic planning agenda. The E P A recognizes the role of PAC in the prevention of pollution and has invited C P A C to showcase the work of our sponsors at this symposium. Many C P A C sponsors have led the way in instituting pollution prevention policies in the past and have expressed their desire to continue to take the lead in this area. Plant safety and the prevention of pollution are of vital concern to industry today. The EPA is also concerned with the reduction of total releases and transfers of 17 highpriority chemicals targeted from the Toxic Release Inventory (15). This inventory, part of the Emergency Planning & Community Right-To-Know Act, requires all manufacturing companies that use certain levels of chemicals to detail how much they emit into the environment (16). The U.S. Chemical industry, petroleum refining, and instrument manufacturers are among the 600 companies being asked by the EPA to voluntarily cut emissions of routinely used toxic chemicals. Tallies of 1988 reports show that the chemical companies, which release the greatest amounts of toxic chemicals, are also the facilities making the greatest reductions in emissions and waste reduction (17). The chemical industry had the greatest amount of pollution reduction of any single industry group (17). Most of the


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reported reductions were achieved by equipment changes, on-site recycling and housekeeping improvements. An equally important part of this mission is the education of the next generation of scientists and engineers who will carry out the fundamental work needed to advance sensing technology for pollution prevention. The S A B also recommends that [the] "EPA...train a professional workforce to help reduce [environmental risks]..." (JO). The D O E is also aware of the growing shortage of appropriately trained scientists and engineers to address the assessment and restoration of its contaminated facilities (JJ). Solutions to environmental problems will require a team approach similar to that found in process analytical chemistry. Scientists working on these problems will have to be familiar with a variety of disciplines, and will need to be able to communicate with other scientists and engineers on the team. This new paradigm is taking hold by a variety of means. In addition to the contact with industrial scientists and engineers that our graduate students have at semiannual meetings and throughout the year, students participate in internships at the sponsor companies and government laboratories. In the past, a common complaint of C P A C sponsors about new analytical graduates, in general, is that they are theory- and technique-oriented, as opposed to problem-oriented, and they are unprepared for real-world processes. To better prepare our students, we have created a new graduate course in process analytical chemistry that incorporates actual case studies presented by sponsor representatives. Students are given a set of measurement objectives and operating constraints for an actual process, and then work in small groups of chemists and chemical engineers to propose an analytical solution. This course offers a unique opportunity for students to be exposed to "real" problems and compare their ideas with the solutions prescribed by working professionals. As part of the Environmental Initiative, C P A C is expanding its educational activities to include courses in environmental sensing and expanding its student intern program to environmental agencies. Today, C P A C has successfully grown to 50 industrial and National Laboratory sponsors, including the Office of Modeling, Monitoring Systems and Quality Assurance (EPA) (18). The National Science foundation has identified C P A C as one of its top two Centers based on the number of sponsors and scientific merit of the research (J). Meanwhile, interest in the potential applications of process analytical chemistry continues to expand. As advances in P A C are revolutionizing industrial chemical processes, we feel that they will also make a significant contribution toward pro-active environmental protection. The time has arrived to move beyond the "postmortem" mode of analysis and institute "front-end" control for pollution prevention.

Literature Cited 1. Scott, C.S. "A Comprehensive Historical Profile of the Center for Process Analytical Chemistry (CPAC): The NSF University/Industry Cooperative Research Center Located at the University of Washington," Div. Ind. Sci. & Tech. Innov., NSF, 1991. 2. Illman, D.L. Trends in Anal. Chem. 1986, Vol. 5, no. 7.


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7. 8.


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11. 12. 13. 14. 15. 16. 17. 18.

Riebe, M.T.; Eustace, D.J. Anal. Chem. 1990, 62, 65A. Jacobs, S.M.; Mehta, S.M. Am. Lab. 1987, 20(11), 15. Callis, J.B.; Illman, D.L.; Kowalski, B.R. Anal. Chem. 1987, 59, 624A. "Survey of Measurement Needs in the Chemical and Related Industries," (TN 1087), NIST, Superintendent of Documents, U.S. Government Printing Office, Washington, DC. Lepkowski, W. "Revolutionary New Regulations, Law On Tap for Plant Safety," C&EN, July 30, 1990, p. 15. Ainsworth, S.J. "Plant Disasters Fuel Industry, Government Concern Over Safety," C&EN, October 29, 1990, p. 7. Reilly, W.K. "Aiming Before We Shoot: The Quiet Revolution in Environmental Policy," The National Press Club, Washington, DC, September 26, 1990. US EPA, "Reducing Risk: Setting Priorities and Strategies For Environmental Protection, The Report of The Science Advisory Board: Relative Risk Reduction Strategies Committee," (SAB-EC-90-021), September 1990. US DOE, "Basic Research for Environmental Restoration," (DOE/ER-0482T), December 1990. US OTA, "Complex Cleanup: The Environmental Legacy of Nuclear Weapons Production," (OTA-O-484), February 1991. Ember, L.R. "Rising Pollution Control Costs May Alter EPA'S Regulatory Direction," C&EN, February 18, 1991, p. 25. Ember, L.R. "Economic Incentives for Environmental Protection," C&EN, March 25, 1991, p. 15. US EPA, Office of Toxic Substances, "Toxics in the Community: 1988 National and Local Perspectives," (EPA 560/4-90-017), September 1990. US EPA, "Chemicals in Your Community: A Guide to the Emergency Planning and Community Right-to-Know Act," (OS-120), September 1988. Hanson, D.J. "EPA'S Emissions Inventory Shows Some Pollution Reduction," C&EN, October 22, 1990, p. 15. Newman, A.R. Anal. Chem. 1990, 62, 965A.

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The Role of Process Analytical Chemistry in Pollution Prevention

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