Fourier-transform infrared spectroscopy sample requirements

Fourier transform infrared spectroscopy FT-IR. The measurement of individual degradation products with FT-IR is very simple, quick and precise. A reference sample spectrum of new oil is required to subtract electronically from the oil sample spectrum. The spectra of the fresh oil and the used oil sample are obtained individually in the same cell. The results - both spectra and the "differential" spectrum are stored in the computer in absorbance format, a form that varies linearly with concentration. 

Conclusions from the Case Study. Exercises such as these are quite common in the characterization of complex solids and do indeed require the combined expertise of a group of specialists. The set of techniques required varies from case to case, but the more or less standard combination of two or more complementary techniques as part of the arsenal is very useful. In retrospect, we were able to identify the techniques which were crucial to solving this problem XPS/TEM, LEIS, XRD and EXAFS. A number of others (Magic-Angle-Spinning NMR (MAS-NMR), Raman Spectroscopy and FTIR (Fourier Transform Infrared Spectroscopy) were applied, but did not add significantly to the final result. The study of various samples which were synthesized in different ways and which showed different catalytic activities did prove relevant, but is not described in detail here. 

Additionally, a variety of analytical equipment and techniques that allow the examination of small- (and micro-) scale microbial cultures and their products have become available. Examples include near infrared and Fourier transform infrared spectroscopy, which offer the ability for in situ detection of specific compounds in fermentation broth [22]. However, sensitivity and the required sample volumes pose serious obstacles that still have to be overcome. Another alternative is offered by sensitive pyrolysis mass spectroscopy, which was demonstrated to be suitable for quantitative analysis of antibiotics in 5-pl aUquots of fermentation broth when combined with multivariate calibration and artificial neural networks [91]. The authors concluded that a throughput of about 12,000 isolates per month could be expected. Furthermore, standard chromatographic methods such as gas chromatography or high-performance liquid chromatography, possibly in combination with mass spectroscopy (MS) for detection, can provide simultaneous quantitative detection of many metabolic products. 

Fourier transform infrared spectroscopy (FTIR) had its origins in the interferometer developed by Michelson in 1880 and experiments by astrophysicists some seventy years later. A commercial FTIR instrument required development of the laser (1960, by Theodore H. Maiman [1927- ], Hughes Aircraft), refined optics, and computer hardware and software. The Fourier transform takes data collected in time domain and converts them to frequency domain, the normal infrared (IR) spectrum. FTIR provided vasdy improved signal-to-noise ratios allowing routine analyses of microgram samples. 

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... 

Advantages of Fourier transform infrared spectrometers are so great that it is nearly impossible to purchase a dispersive infrared spectrometer. Fourier transform visible and ultraviolet spectrometers are not commercially available, because of the requirement to sample the interferometer at intervals of S = l/(2Av). For visible spectroscopy, Av could be 25 000 cm 1 (corresponding to 400 nm), giving S = 0.2 im and a mirror movement of 0.1 xm between data points. Such fine control over significant ranges of mirror motion is not feasible. 

Chemical and instrumental (e.g., chromatography and mass spectrometry) methods have provided valuable information that lead to the advancement of cheese science. However, these techniques suffer from one or more of the following problems (1) the extensive use of solvents and gases that are expensive and hazardous, (2) high costs, (3) the requirement of specific accessories for different analytes, (4) the requirement of extensive sample preparation to obtain pure and clean samples, and (5) labor-intensive operation. These disadvantages have prompted for the evaluation and adoption of new, rapid, and simple methods such as Fourier-transform infrared (FTIR) spectroscopy. Many books are available on the basics of FTIR spectroscopy and its applications (Burns and Ciurczak, 2001 Sun, 2009). FTIR spectroscopy monitors the vibrations... 

The most widely available technique for identifying mainly polymer, but also additives in plastics, is Fourier Transform Infrared (FTIR) spectroscopy. Samples are exposed to infrared light (4000-400 wavelengths per centimetre or cm ) causing chemical bonds to vibrate at specific frequencies, corresponding to particular energies. In the last 5 years, an accessory for FTIR has been developed, which enables non-destructive examination of surfaces and so is ideal for analysis of plastics in museum collections. Attenuated Total Reflection-FTIR (ATR-FTIR) requires samples to be placed on a diamond crystal with a diameter of 2 mm through which the infrared beam is reflected... 

There was also described and discussed the relatively new Fourier transform infrared emission spectroscopy (IRES), its principle, an appropriate FT-IRES setup and applications. FT-IRES is unique in that it does not require an external radiation source, because the sample itself is the source. The radiation emitted from the sample is collected and sent to the detector. The ratio of the sample signal to that from a black body source represents the spectrum. However, appli-... 

Infrared emission spectroscopy forms a valuable technique that can be plied in situ during the heat treatment. The technique of measurement of discrete vibrational frequencies emitted by thermally excited molecules, known as Fourier transform infrared emission spectroscopy (FTTR ES, or shortly lES) has not been widely used for the study of materials. The major advantages of lES are that the samples are analyzed in situ at increasing temperatures and lES requires no sample treatment other than that the sample should be of submicron particle size. Further, the technique removes the difficulties of heating tiie sample to temperatures where reactions take place with subsequent quenching prior to the measurement, because lES measures the process as it is actually taking place. 

A fast, direct and non-destructive method involving no sample preparation was developed for recording a well-resolved and reproducible spectmm of special acrylic fibre (SAF), a precursor for carbon fibre using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. A novel method was developed for determining the composition of SAF containing both acrylate and carboxylic acid comonomers. The special feature is that no standard samples (of known composition) are required. 11 refs. 

Fourier transform infrared speetroseopy (FTIR) is a modem method for last analysis of phenolic resins [204,226,227], the modilied products [33,148,183,214], the curing process [218], and the erosslinked products. Several FTIR techniques are useful in phenolic resin characterization. The simplest method is transmission spectroscopy. This method requires an optimum optical density of the sample. Soluble prepolymers and soluble products may be examined as solutions using solvents i.e. triohloromethane, that are reasonably transparent over the range of400-4000 cm. Absorbance measurements can also be made on a thin film prepared by casting from solution. Solid, insoluble products may be mixed with potassium bromide and compessed at room temperature to an optical clear disk that can measured using the transmission method. 

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