FTIR remote

Alternatively, it is possible to install fibre optic probes directly in the main stream in-line while the IR spectrophotometer remains remotely in a low vibration laboratory environment. In-line analysers, which do not remove any sample from the line, have the minimum possible lag time and do not change the sample physically or chemically from its nature in the process. Recently, bundles of 500 /xm optic fibres have been developed for the 5000-900 cm (2000-11,000 nm region), which permit transmission of IR energy over distances of several metres. Lowry et al. [76] have evaluated fibre-optic cables that might prove useful in FTIR remote sampling applications. The various optical fibres (chalcogenide, silver halide, heavy metal fluoride or sapphire) differ in their spectral window [77]. Due to the thermal stability and the spectral window, sapphire fibres are considered suitable for in-line characterisation of polymer melts in a production line (e.g. in an extruder head) as an alternative to discontinu-ously operating conventional off-line transmission IR spectroscopy of polymer films [78]. 

It is becoming more and more desirable for the analytical chemist to move away from the laboratory and iato the field via ia-field instmments and remote, poiat of use, measurements. As a result, process analytical chemistry has undergone an offensive thmst ia regard to problem solviag capabihty (77—79). In situ analysis enables the study of key process parameters for the purpose of definition and subsequent optimization. On-line analysis capabihty has already been extended to gc, Ic, ms, and ftir techniques as well as to icp-emission spectroscopy, flow iajection analysis, and near iafrared spectrophotometry (80). 

Carlson, R. C. Hayden, A. F. Telfair, W. B., Remote observations of effluents from small building smokestacks using FTIR spectroscopy, Appl. Opt. 1988, 27, 4952 4959... 

Diisocyano- azulene One NC group bonded to surface in p mode the second one is free and remote from the surface 2116, 2125 2117 uncoord NC 2163 coord NC FTIR [33]... 

Table 11.2 summarizes the detection limits for FTIR measurements in the atmosphere for some gases of interest. Typical concentrations of each in remote to polluted atmospheres are discussed below with respect to the individual species however, in general, it can be stated that FTIR is most suitable for measuring... 

FTIR, TDLAS, and LIF are in situ techniques, whereas DOAS is a long-path method that gives only a path-integrated result. NO, N02, NO,3, and HONO have been successfully measured with DOAS even in rural and remote regions. PAN, HN03, and NH3 have been measured with FTIR in urban areas, but its sensitivity at present is not adequate for levels below a few parts per billion by volume. NO, N02, PAN, HN03, and NH3 have been measured with TDLAS down to sub-ppbv levels. A review with references for applications of these three methods is available (13). The LIF method has been more recently developed, has been applied to the measurement of NO, N02, NH3, and HONO (see reference 14 for an example), and offers sensitivity down to the parts per trillion by volume level. 

Raman is simple to use and require virtually no sample preparation. The vibrational spectra of polymer samples in their original forms can be measured and casting or hotpressing of the material into thin films (commonly used for FTIR measurements), a very time-consuming procedure that can affect the original structure of the material, are not required. It also offers remote analysis capabilities if combined with fibre optics [108, 109]. Accurate determination of contaminant content in recycled polymeric resins have been reported in the literature [110, 111, 112]. 

Francis P., Burton M., and Oppenheimer C. (1998) Remote measurements of volcanic gas compositions by solar FTIR spectroscopy. Nature 396, 567-570. 

The selection of the microscopic area for FTIR microspectroscopy is achieved by a remote aperture located between the objective and detector. The remote aperture commonly has a rectangular opening with two pairs of knife-edged blades. The blades are often made from a material that is transparent to visible light but opaque to infrared light. 

Capillary columns are used to separate 1,1,1-trichloroethane from the other components in a mixture. Capillary columns provide wider versatility offering superior resolution of components. A comparison of capillary and packed column for analysis of volatile organics by GC is available (Clark and Zalikowski 1990). Narrow-bore capillary columns have high resolving power but may not be suitable for headspace analysis because of easy column saturation (Ohno and Aoyama 1991). Wide-bore capillary columns are suitable in such cases (Ohno and Aoyama 1991). Different detectors can be used ECD, HECD, and MS have been described. The MS is the most selective detector, but the HECD is the most sensitive. Both closed path and open path Fourier transform infrared spectrometry (FTIR) have recently been used for the determination of 1,1,1 -trichloroethane in air (Carter et al. 1992 Trocha and Samimi 1993 Xiao and Levine 1993). Although the FTIR methods have higher detection limits than some of the other conventional methods, they afford the opportunity of remote monitoring of real-time samples (Xiao and Levine 1993). 

FTIR has become more portable in recent years due in part to the miniaturisation of the interferometer. However, FTIR instruments have only recently been reduced in size to the same extent as UV-Vis or NIR devices. D P Instruments has developed the Model 102 portable interferometer-based FTIR spectrometer (Figure 7.6) for use in remote sensing applications. Weighing less than 7 kg, it can run off batteries or a mains supply. A PC is built into the case along with the FTIR module. The spectral range is 625-5000cm with a resolution of 4 cm... 

Optical remote sensing (ORS) technologies, employing infrared spectral analysis techniques, have been utilized in the development of chemical agent standoff detection technologies. Within the ORS technologies, there are two types of remote sensing systems passive and active (laser). The section below only looks at the passive system, which employs a Fourier Transform Infrared (FTIR) spectrometer. 

ACAMS Automated Continuous Air Monitoring System Remote molecular air quality monitoring system (FTIR) Nerve agent vapor detector (NAVD)... 

Even the introduction of the FTIR technique did not increase the analytical value, but since the size of the sample for detection was reduced from 1 mg to 1 ng, the FTIR method was adapted for the detection of alkanes produced and analysed by other analytical methods, i.e. pyrolysis-FTIR" (see also Sections IV and V). Specific gas alkane molecules such as CH4, C2H6 and C3H8 are individually identified, therefore the use of FTIR gas cell permits continuous monitoring of these, in flight. This system, although designed for flow through cell detection, can be employed for remote sensors. 

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