Commercial Fourier transform

Commercial Fourier transform spectrometers operating at moderate resolution (1cm-1) require fractions of seconds to complete a scan of the interferometric mirror (scans may only take tens of milliseconds if only low spectral resolution is required). A new strategy must now be used to study the... 

The introduction of commercial Fourier transform (FT) spectrometers in the early 1960 s has made it possible, in part, to overcome the limitations associated with dispersive instruments and has helped to broaden the scope of problems amenable to investigation by infrared spectroscopy. The purpose of this review is to compare the performance of FT and dispersive spectrometers and to illustrate areas of application in which FT spectroscopy has proven advantageous for the study of adsorbed species. In view of these objectives only a limited treatment of the theory underlying FT spectroscopy will be presented here. 

The situation, however, is different for the infrared spectroscopic measurements with opposed anvil cells. The source beam in commercial Fourier transform infrared spectrometers is generally focused to about 1 cm diameter at the sample, whereas the diameter of the gasket hole in the high pressure cell is only about 0.3 mm. Therefore, a source beam condensing system is required in order to obtain infrared spectra with a good signal-to noise ratio. Commercial beam condensers (4X, 6X) could, in principle, be adapted for these purposes. In practice, however, the mirrors of the... 

The use of data-processing equipment in conjunction with infra-red spectrophotometers, both dispersive and interferometric, produces three advantages, namely instrument control, spectrum manipulation, and spectrum identification and interpretation. Firstly, the control of the instrument is simplified and the reproducibility and accuracy of wavelength and transmission (or absorbance) are greatly enhanced. For example, one commercial Fourier transform instrument uses a helium-neon laser to obtain an accuracy of better than 0.01 cm at 4000cm, whereas older dispersive instruments could have an error of 50 cm The accuracy of... 

Table 2. Survey of commercial Fourier transform spectrometers... 

In virtually all types of experiments in which a response is analyzed as a function of frequency (e.g., a spectrum), transform techniques can significantly improve data acquisition and/or data reduction. Research-level nuclear magnetic resonance and infra-red spectra are already obtained almost exclusively by Fourier transform methods, because Fourier transform NMR and IR spectrometers have been commercially available since the late 1960 s. Similar transform techniques are equally valuable (but less well-known) for a wide range of other chemical applications for which commercial instruments are only now becoming available for example, the first commercial Fourier transform mass spectrometer was introduced this year (1981) by Nicolet Instrument Corporation. The purpose of this volume is to acquaint practicing chemists with the basis, advantages, and applications of Fourier, Hadamard, and Hilbert transforms in chemistry. For almost all chapters, the author is the investigator who was the first to apply such methods in that field. 

As was true with infrared and nuclear magnetic resonance instruments. Fourier transform mass spectrometers provide improved signal-to-noisc ratios, greater speed, and higher sensitivity and resolution." Commercial Fourier transform mass spectrometers appeared on the market in the early 1980s and are now offered by several manufacturers. 

More recently, we have improved the time-resolution of the system substantially. The present instrument is capable of recording high time- and frequency-resolution spectra of transients having decay times from the nanosecond to the millisecond regime. The minimum time delay between the initiation of the transient and the first spectral observation can be arbitrarily short. (Typically, the first spectrum is recorded just before the transient in order to provide a background observation. A maximum of 128 successive time-delayed spectra of a single transient can be recorded the minimum time delay between each of these is 10 ns. All operational parameters (resolution, sensitivity, etc.) of the commercial Fourier transform spectrometer with which the system is used, are unchanged by time-resolved operation. Variability in die baseline due to amplitude instabilities in the excitation source (usually a pulsed laser) are taken into account, and appropriate corrections are made. 

Data processing programs for the above-mentioned purposes are often supplied with commercial Fourier transform-infrared (FT-IR) spectrometers as integral parts of their software packages. They are also available in commercial software packages... 

Most commercial Fourier-transform (FT) spectrometers are based on the Michelson interferometer (Figure 3). A collimated beam of radiation falls on a beam splitter that divides it into two beams with approximately equal intensities. These two beams strike mirrors that return them to the beam splitter where they recombine, creating interference, and... 

The aim of this work is the determination of several nutritional parameters, such as Energetic Value, Protein, Fat, and Carbohydrates content, in commercially available yoghurt samples by using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FT-IR) spectrometry and a partial least square approach. 

C fourier-transform nmr commercially available following first ob.servation of C nmr signal by P. C. Lauterbur and by C, H, Holm in 1957,... 

Time-resolved Fourier transform infrared spectroscopy has been used surprisingly little considering the nuadter of commercial spectrometers that are currently in laboratories and the applicability of this technique to the difficult tine regime from a few is to a few hundred is. One problem with time-resolved Fourier transform spectroscopy and possibly one reason that it has not been more widely used is the stringent reproducibility requirement of the repetitive event in order to avoid artifacts in the spectra( ). When changes occur in the eiaissirr source over the course of a... 

Several commercial companies now offer process compatible NMR systems. These systems are either low resolution based on relaxation time measurements or high resolution Fourier Transform spectral measurements. The low resolution systems are manufactured by Process Control Technologies (www.pctnmr.com) and Progression, Inc. (www.progression-systems.com). Progression s systems... 

Ion detection is carried out using image current detection with subsequent Fourier transform of the time-domain signal in the same way as for the Fourier transform ion cyclotron resonance (FTICR) analyzer (see Section 2.2.6). Because frequency can be measured very precisely, high m/z separation can be attained. Here, the axial frequency is measured, since it is independent to the first order on energy and spatial spread of the ions. Since the orbitrap, contrary to the other mass analyzers described, is a recent invention, not many variations of the instrument exist. Apart from Thermo Fischer Scientific s commercial instrument, there is the earlier setup described in References 245 to 247. 

Non-ionic surfactants of a commercial washing powder were separated by supercritical fluid chromatography (SFC) and determined by APCI-MS. The constituents were first extracted by supercritical fluid extraction (SFE) using C02 with or without methanol as a modifier. Variations of the conditions resulted in a selective extraction of the analytes, which could be determined without further purification. Six groups of surfactants were observed, four of which are alkyl-polyethoxylates. The presence of APEO could be excluded by identification recording SFC-FTIR (Fourier transform infrared) spectra [31]. 

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