Commercial NIR instrumentation

J.J. Workman and D.A. Burns, Commercial NIR Instrumentation, in Handbook of Near-Infrared Analysis, 2nd edn, D.A. Burns and E.W. Ciurczak (eds), Marcel Dekker, New York, 2001. 

The earliest commercial NIR instrumentation was based upon filters. (Karl Norris used a UV/Vis/NIR scanning Cary instrument, although that instrument wasn t designed for NIR, per se.) A filter is a window that allows a particular slice of the spectrum to pass through (a bandpass filter) or blocks all wavelengths below or above a certain frequency (edge and cutoff filters). 

JJ Workman and DA Bums. Commercial NIR Instrumentation. In DA Burns and EW Ciurczak, eds. Handbook of Near Infrared Analysis. New York Marcel Dekker, 2001, pp. 53-71. 

Types of Sample Presentation Devices Available from Commercial NIR Instrument Manufacturers ... 

Presenting nearly 50% new and revised material, this thoroughly updated edition incorporates the latest advances in instrumentation, computerization, calibration, and method development in NIR spectroscopy. The book underscores current trends in sample preparation, calibration transfer, process control, data analysis, and commercial NIR instrumentation. New chapters highlight novel applications including the analysis of agro-forestry products, polymers, blood, and control serum. They also cover NIR spectra, process analytical technologies (PAT), quantitative and qualitative analyses for nutraceuticals, NIR photography uses in medicine, and counterfeit detection methods for various applications. 

Workman JJ, Burns DA. Commercial NIR instrumentation. In Burns DA, Ciurczak EW, editors. Handbook of Near-Infrared Analysis. 2nd ed. New York Marcel Dekker 2001. 

Commercially available instrumentation for absorbance and fluorescence measurements in the NIR region is scarce. Conventional absorbance spectrophotometers... 

Standardization The instrument response function can vary from analyzer to analyzer. If calibration transfer is to be achieved across all instrument platforms it is important that the instrument function is characterized, and preferably standardized [31]. Also, at times it is necessary to perform a local calibration while the analyzer is still on-line. In order to handle this, it is beneficial to consider an on-board calibration/standardization, integrated into the sample conditioning system. Most commercial NIR analyzers require some form of standardization and calibration transfer. Similarly, modem FTIR systems include some form of instrument standardization, usually based on an internal calibrant. This attribute is becoming an important feature for regulatory controlled analyses, where a proper audit trail has to be established, including instrument calibration. 

The use of hber optics and hber-optic multiplexing can increase the number of analysis points, and hence can reduce the overall costs related to a single analyzer. This approach has been used successfully with NIR instrumentation, where typically up to eight points can be handled. As noted earlier, the use of hber optics with IR Fourier transform instruments has in the past been limited. New hber materials with improved optical throughput are available, and also with the considered use of IR lasers, the role of hbers for IR applications is expected to increase. Although in the past commercial multiplexers have been available for mid-lR hber systems, their use has not been widespread. 

It is no coincidence, then, that several companies specializing in NIR equipment should spring up in nearby communities of Maryland over the years [12]. In fairness, Dickey-John produced the first commercial NIR filter instrument, and Technicon (now Bran + Leubbe) the first commercial scanning (grating) instrument. Available instruments and the principles of operation of each type are covered in a later chapter. However, before looking at the hardware, it is necessary to understand the theory. 

Another application to pre- and newborns was published by Liu et al. in 1997 [95]. In this paper, they presented a measure of fetal lung maturity from the spectra of amniotic fluid. The lecithin/spingomyrlin (L/S) ratio was determined by thin layer chromatography (TLC) and used to calibrate a NIR equation using the whole amniotic fluid extracted from pregnant women. About 350 iL of fluid was required. This was scanned from 400 to 2500 nm using a commercially available instrument. The correlation between further samples of fluid and TLC results was about 0.91, considered excellent for the complexity of the solution and extremely small sample size. Of course, a PLS equation was needed due to the complex nature of the samples. 

Many spectroscopic techniques are nowadays used for surface investigations. Some of them (i.r., Raman, u.v.-VIS-NIR), do not need particular modifications of commercially available instruments and so their use is common. As a consequence, the number of papers that have appeared in the recent literature (1975-1981) describing i.r., Raman and u.v.-VIS-NIR spectra of adsorbed species is so large that an exhaustive review is practically impossible. In this review we shall not attempt to give a complete examination of all contributions and we focus our attention on those where the structure of both the surface sites and surface species is taken into consideration. The reasons for this can be summarized as follows (/) many papers only report the spectra of surface species for analytical purposes and so no detailed discussion is given about the assignment (ii) many papers report the spectra only as ancillary data, able (in principle) to support hypotheses obtained through other surface methods (Hi) in many papers the examined solids are so complex (because they are or are similar to industrial catalysts) that a detailed discussion of the surface structures is nearly impossible. The boundary between the two types of contributions is labile and as a consequence the choice quite subjective. 

Very surface sensitive MIR fiber optics are hmited in range, expensive, and fragile Remote sensing difficult Commercial MIR instmments slower than NIR instruments Limited information in this range—overtone vs. fundamental peaks... 

Various kinds of surface chemistries for solubilization, functionalization, and bioconjugation of UCNPs have been reported [6]. However, routine instrumentation for this technology is not readily available. Most fluorometers still need to be adapted to NIR laser excitation, and respective microplate readers have not yet been commercialized. However, instrumentation for fluorescence microscopy of UCNPs has recently become available (www.leica.com). 

Fixed Fiiters. A schematic of a fixed-filter (FF) spectrometer (FFS) is shown in Figure 4.1.6A. The first commercial NIR analyzers were of this type and were used at grain elevators, where wet chemistry was not timely enough to be of use. Today several companies produce multiple FF instruments. The QUlK/20, incorporating 20 narrow-band interference filters (shown in Fig. 4.1.6B), is typical of theFF technology. It has a filter wheel with 20 filters and implements a noise reduction routine based on the fast Fourier transform (8, 20, 38). 

Fourier Transform-Near infrared (FT-NiR). Only within the last 20 years has FT-NIR instrumentation (Fig. 4.1.14) become available. Even then, the first commercial instmments had a distinct disadvantage compared to grating-based scanning instruments. FT-NIR spectrometers employ an entirely different method for producing spectra. There is no dispersion involved. Energy patterns set up by an interaction with a sample and a reference and moving mirrors (or other optical components) produce sample and reference interferograms that are used to calculate the absorbance spectrum of the sample. 

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