Fourier transform infrared instruments

Fourier transform infrared instruments provide a more convenient beam geometry—circular rather than slit shaped—at the sample focus. 

Apart from innovative ideas in chemistry, progress in the field of matrix i.solation is closely coupled with the development of new instruments and devices. Fourier-transform infrared instruments have enormously increased the amount of information which is obtained from matrix-isolation experiments. With new helium-cooled infrared detectors and faster Fourier-transform processors, less time is required to obtain high-quality spectra over a large spectral range. Unusual species at low concentrations and isotopic molecules with a low natural abundance can therefore now be detected. Additionally, hidden data are easily accessible by spectra subtraction (e.g., of the spectra before and after photolysis). 

Interferometer A nondispersive device that obtains spectral information through constructive and destructive interference used in Fourier transform infrared instruments. 

Tenn. Electronic spectroscopy was performed on a Varian Cary 17 recording spectrophotometer and a Nicolet Fourier Transform Infrared instrument was used to record spectra between 4000 and 200 cm l of samples in Csl. Electrical measurements were performed at room temperature on compacted samples by a four probe technique. TGA was performed on a DuPont 990 Analyzer using a DuPont 951 TGA module. TGA for the GC/MS analysis was performed on a DuPont 950 instrument. Volatile products were collected in a Tenax containing tube which was attached to the GC inlet port, GC/MS was performed on a Hewlett Packard 5982A coupled to a 5934A data system. DSC was performed on a DuPont 1090 analyzer using a DuPont 910 DSC module. 

The most important metal-containing heat stabilizers in PVC can also be identified through IR-spectroscopy (see Section 8.2). Characteristic absorption bands for the salts of carboxylic acids are the bands of the ionized carboxy group in the region from 1590 to 1490 cm and from 1410 to 1370 cm Since the exact position of the absorption bands depends mainly on the metal counterions of the carboxy group, the IR-spectra provide a first identification of these metals. Tin stabilizers also show characteristic bands in these regions of the IR-spectrum. To determine the spectra, one uses pressed pellets made by finely grinding the sample material with potassium bromide. The identification of the metal becomes even more certain if an FT-IR (Fourier Transform/Infrared) instrument is available. With such an instrument, it is possible to subtract the spectrum of an additive-free... 

In addition to covering Raman microscopy, this book has a wealth of information on Raman instrumentation in general. Elving P J and Winefordner J D (eds) 1986 Fourier Transform Infrared Spectroscopy (New York Wiley)... 

Two common detectors, which also are independent instruments, are Fourier transform infrared spectrophotometers (FT-IR) and mass spectrometers (MS). In GC-FT-IR, effluent from the column flows through an optical cell constructed... 

Fourier transform infrared (FTIR) analyzers can be used for industrial applications and m situ measurements in addition to conventional laboratory use. Industrial instruments are transportable, rugged and relatively simple to calibrate and operate. They are capable of analyzing many gas components and determining their concentrations, practically continuously. FTIR analyzers are based on the spectra characterization of infrared light absorbed by transitions in vibrational and rotational energy levels of heteroatomic molecules. 

Fig. 19.3 Layout of a Fourier-transform infrared spectrometer. Reproduced by permission of Lloyd Instruments PLC, Warsash, Southampton S03 6HP.

Fourier-transform infrared (IR) spectra (resolution 2 cm- ) were recorded with a Perkin Elmer 1750 instrument in a quartz cell connected to grease-free evacuation and gas manipulation lines. The self-supporting disk technique was used. Before recording the spectra, the samples were treated with O2 at 450°C (Ih), then cooled down to r.t. before evacuating the O2. The sample was then evacuated at 400°C. Evacuation at higher temperatures lead to a drastic cut off of IR trasparency. All reactants were purified prior to the adsorption experiments. Due to the better resolution of the spectra, only results for Sb V=1.0 are reported here, however the IR data for Sb V=3.0 were not significantly different. 

Several additional instrumental techniques have also been developed for bacterial characterization. Capillary electrophoresis of bacteria, which requires little sample preparation,42 is possible because most bacteria act as colloidal particles in suspension and can be separated by their electrical charge. Capillary electrophoresis provides information that may be useful for identification. Flow cytometry also can be used to identify and separate individual cells in a mixture.11,42 Infrared spectroscopy has been used to characterize bacteria caught on transparent filters.113 Fourier-transform infrared (FTIR) spectroscopy, with linear discriminant analysis and artificial neural networks, has been adapted for identifying foodbome bacteria25,113 and pathogenic bacteria in the blood.5... 

With recent developments in analytical instrumentation these criteria are being increasingly fulfilled by physicochemical spectroscopic approaches, often referred to as whole-organism fingerprinting methods.910 Such methods involve the concurrent measurement of large numbers of spectral characters that together reflect the overall cell composition. Examples of the most popular methods used in the 20th century include pyrolysis mass spectrometry (PyMS),11,12 Fourier transform-infrared spectrometry (FT-IR), and UV resonance Raman spectroscopy.16,17 The PyMS technique... 

Several modem analytical instruments are powerful tools for the characterisation of end groups. Molecular spectroscopic techniques are commonly employed for this purpose. Nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and mass spectrometry (MS), often in combination, can be used to elucidate the end group structures for many polymer systems more traditional chemical methods, such as titration, are still in wide use, but employed more for specific applications, for example, determining acid end group levels. Nowadays, NMR spectroscopy is usually the first technique employed, providing the polymer system is soluble in organic solvents, as quantification of the levels of... 

In-situ Fourier transform infrared spectroscopy. The final technique in this section concerns the FTIR approach which is based quite simply on the far greater throughput and speed of an FTIR spectrometer compared to a dispersive instrument. In situ FTIR has several acronyms depending on the exact method used. In general, as in the EMIRS technique, the FTIR-... 

The pharmaceutical industry comprises the largest segment, roughly 15 to 20%, of the infrared (IR) market. Modern mid-infrared instrumentation consists almost exclusively of Fourier transform (FT) instruments. Because of its ability to identify molecular species, FT-IR is routinely used as an identification assay for raw materials, intermediates, drug substances, and excipients. However, the traditional IR sample preparation techniques such as alkali halide disks, mulls, and thin films, are time-consuming and not always adequate for quantitative analysis. 

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