Process vibrational spectroscopy instrument

Having seen the number of papers devoted to bioprocess analyses utilizing vibrational spectroscopy, it cannot be considered an experimental tool any longer. Manufacturers are responding to pressure to make their instruments smaller, faster, explosion-proof, lighter, less expensive, and, in many cases, wireless. Processes may be followed in-line, at-line, or near-line by a variety of instruments, ranging from inexpensive filter-based to robust FT instruments. Raman, IR, and NIR are no longer just subjects of feasibility studies they are ready to be used in full-scale production. 

Implementing this level of automation intelligence has been the most difficult to realize within manufacturing industries. That is, while automation controls integration of simple univariate instruments (e.g., a hlter photometer) is seamless, it is much more problematic for multivariate or spectral instruments. This is due to the tower of babble problem with various process spectroscopic instraments across process instrument manufactures. That is, the communications protocols, wavelength units and hie formats are far from standardized across spectral instruments, even within a particular class of techniques such as vibrational spectroscopy. Several information technology (IT) and automation companies have recently attempted to develop commercialized solutions to address this complex problem, but the effectiveness of these solutions has yet to be determined and reported. 

Vibrational spectroscopy, in the form of mid-IR, NIR and Raman spectroscopy has been featured extensively in industrial analyses, both quality control (QC), process monitoring applications and held-portable applications [1-6]. The latter has been aided by the need for advanced instrumentation for homeland security and related HazMat applications. Next to chromatography, it is the most widely purchased classihcation of instrumentation for these measurements and analyses. Spectroscopic methods in general are favored because they are relatively straightforward to apply and to implement, are rapid in terms of providing results, and are often more economical in terms of service, support and maintenance. Furthermore, a single spectrometer or spectral analyzer, in a near-line application, may serve many functions, whereas chromatographs (gas and liquid) tend to be dedicated to only a few methods at best. 

Stark, E.W., Near-Infrared Array Spectrometers. In Chalmers, J.M. and Griffiths, P.R. (eds), Handbook of Vibrational Spectroscopy, vol 1 John Wiley 8c Sons New York, 2002, pp. 393-422. Goldman, D.S., Near-Infrared Spectroscopy in Process Analysis. In Meyers, R.A. (ed.), Encyclopedia of Analytical Chemistry, vol 9 Process Instrumental Methods John Wiley 8c Sons New York, 2000, pp. 8256-8263. 

For process control, analytical techniques such as vibrational spectroscopies, which provide information about paint composition, are important based on (1) the popularization of FT instruments, with a better signal-to-noise ratio and fast data acquisition speed (2) reflectance techniques (total attenuated and diffuse), photoacoustic spectroscopy, and the development of optical fiber-based devices that provide easy spectrometric measurements on crude samples (3) vapor-phase generation coupled with FTIR for fast analysis of the volatile paint fractions ... 

A polymeric material coated onto, for example, aluminum is easily measured by an attenuated total reflectance attachment. Vibrational spectroscopy, IR, or NIR may be used for this application. A possible postproduction reaction, polymerization, or coating each may be followed by a surface probe. The reaction requires only a moderately fast instrument, such as a rapid scanning IR or NIR. Monitoring a continuous process, e.g., a lamination of two or more layers, requires a rapidly scanning device. In this case, an interferometric IR/NIR or accoustooptic device is able to scan hundreds to thousands of sample points per minute. 

Even though polymer analysis by vibrational spectroscopy has been common for decades (6-9), the control of the process seems to have been overlooked. Of course, there have never been instruments as sophisticated as those existing today. 

Vibrational spectroscopies (mid-IR, near-IR, Raman) play an important role in polymer/additive analysis. Optical advances as well as spectacular advances in computing technology and data processing algorithms have greatly impacted vibrational spectroscopy over the past 25 years (cfr Table 1.5). Rapid digital data acquisition is required for FTIR, FT-Raman or CCD-Raman spectroscopy. The raw data obtained from these instruments must always be manipulated before a recognisable spectrum can be displayed. 

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