By Terry K. McMahon, CONTROL Columnist
PROCESS ANALYTICAL Technology (PAT) has several meanings, two of which are relevant to this column. To U.S. Food and Drug Administration (FDA) regulators, PAT encompasses technologies that enhance pharmaceutical manufacturing process understanding, controllability and robustness. To the process control community, PAT connotes analytical instrumentation that is applied on-steam, yielding real-time analytical data. The book discussed here uses the latter definition, and further restricts its treatment to spectroscopic methods. Chromatographic, electrochemical and other methods aren’t covered.
Published by Blackwell Publishing Ltd., Process Analytical Technology (451 pages, 2005), was edited by Katherine Bakeev, who also authored the concluding chapter on “Future Trends in Process Analytical Chemistry.” Eighteen other authors, all PhDs or university faculty, contributed the other 11 chapters. This is an excellent compilation of tutorials and hard experience in implementing process analyzers by a distinguished panel of experts. I hesitate to mention only a few for fear of omitting others that are equally significant, but I will do it nevertheless.
But first, I have a few, relatively minor caveats:
- The book’s historical perspective begins in the 1970s, though the field already was more than 30 years old, because Karl Luft and Erwin Lehrer developed and deployed NDIR and paramagnetic oxygen analyzers at I.G. Farbenindustrie in the late 1930s.
- It overlooks the pioneering work done at DuPont on UV spectrophotometry, in the context of its revolutionary chloride process for titanium dioxide in the late 1950s and its subsequent commercialization by DuPont Instruments.
- The statement that, “The PAT Initiative strongly advocates the use and deployment new measurement technology for pharmaceutical manufacturing” is incorrect. This FDA initiative doesn’t advocate specific means, only the end objective of well-understood, controllable and robust processes.
In Chapter 9, “On-Line Applications in the Pharmaceutical Industry,” Doherty and Kettler (Eli Lilly) present a thorough discussion of the PAT Initiative, its history and implications. In Chapter 2, “Implementation of Process Analytical Technologies,” Guenard and Thurau (Merck & Co.) discuss the implementation of PAT in an industrial setting and the differing procedures used in the chemical and pharmaceutical industries.
Ernie Baughman’s “Introduction and Historical Perspective,” Chapter 1, effectively conveys his extensive experience with PAT at Amoco and CPAC, as well as his personal enthusiasm for this technology. He discusses the difficult challenge of direct, inferential measurement of motor fuel octane (MON and RON) by NIR and its later use for Reid vapor pressure, API gravity and other gasoline quality parameters.
John Coates’ chapter, “Infrared Spectroscopy for Process Applications” is an impressive tutorial on this multi-faceted technique. The various types of infrared instrumentation are reviewed, key components are analyzed, and maintenance and sample-handling issues are addressed. The broad range of infrared analysis applications is illustrated.
The longest chapter in the book is Charles Miller’s (DuPont Engineering Technologies) tutorial, “Chemometrics in Process Analytical Chemistry.” Chemometrics s not for the faint of heart, and is described as a labyrinth into which many scholars wandered, never to be heeard from again. Miller’s definition of chemometrics is the application of multivariate, empirical modeling methods to chemical data. It is data-driven, as opposed to theory-driven, and so it requires substantial amounts of reliable data to develop meaningful relationships. Nowhere is this as critical as in deriving models for NIR applications.
Ann Brearley’s (NatureWorks) discussion of near-infrared (NIR) applications in the chemical industry focuses on implementing NIR, including project team organization and economic value determination. The capabilities and limitations of the method are analyzed, and calibration methods are reviewed. Brearley cites a number of case histories primarily from polymer processing applications
Katherine Bakeev’s (GlaxoSmithKline) concluding chapter cites the IFPAC/2002 paper by Rob Dubois (Dow Canada) and Jeff Gunnel (ExxonMobil), which envisions process analytics technology in 2012. Micro-analytical and biosensor developments are discussed. Specific emerging techniques, including thermal effusivity, acoustic spectroscopy and light-induced florescence, are described. Trends in Data Communications, particularly wireless, are likely to be crucial in shaping the future of this technology.
The volume should find a place in the libraries of most process industry firms. It is important that newer practitioners stand on the shoulders of those who have gone before, so mistakes won’t be repeated and new horizons can be reached.
Terrence K. McMahon of McMahon Technology Associates, Leonia, NJ is the "Around the Loop" columnist for CONTROL magazine and ControlGlobal.com. He can be reached at Mcmahontec135@aol.com