Spectrometer continued rapid scanning

Protein Adsorption. The development of medical implant polymers has stimulated interest in the use of ATR techniques for monitoring the kinetics of adsorption of proteins involved in thrombogenesis onto polymer surfaces. Such studies employ optical accessories in which an aqueous protein solution (93) or even ex - vivo whole blood (94-%) can be flowed over the surface of the internal reflection element (IRE), which may be coated with a thin layer of the experimental polymer. Modem FT-IR spectrometers are rapid - scanning devices, and hence spectra of the protein layer adsorbed onto the IRE can be computed from a series of inteiferograms recorded continuously in time, yielding ah effective time resolution of as little as 0.8 s early in the kinetic runs. Such capability is important because of the rapid changes in the composition of the adsorbed protein layers which can occur in the first several minutes (97). 

A new and efficient mode of operation is presented that involves a continuous rapid-scan FTIR spectrometer, the measurement technique relying completely on the utilisation of the digital signal processor for data acquisition and manipulation. Experimental and mathematical details were discussed. Application of the rapid-scan technique was illustrated with some results for a styrene-acrylonitrile/butadiene copolymer. 17 refs. 

For visual observation of the cell interior through the sapphire windows a lamp mounted behind one end is used. A mirror and stereo microscope at the other end facilitate the observation. The microscope is equipped with a normal camera or a video camera. Normally the phenomena within the cell are continuously observed and controlled with video camera and colour monitor. A video recorder serves for documentation, for inspection of short time processes and for the production of standing flame pictures for size and shape determination. Instead of the microscope a Jarrell-Ash diode array rapid scan spectrometer can be attached to the cell to obtain flame spectra in the visible and UV-regions. 

In routine FTIR spectroscopy the spectrometer is operated in continuous scan mode. In this mode of operation, the moving mirror is scanned at a constant velocity, v (cms ), with the light beam path difference at any time, t being given hy 6 = 2 1 (cm). An internal HeNe laser beam is also passed through the interferometer and, since it is essentially monochromatic (I5,798cm ), it is used to accurately calibrate the positions of Mm for data sampling. Continuous scan FTIR is most commonly used to monitor stable samples, but can also be used in rapid-scan mode to monitor time-dependent processes on timescales down to ca. 20 ms. 

As the speed of electronics increased, it became possible to use rapid-scanning interferometers at their lowest scan speed for hyperspectral imaging. The first report of this type of instrument was made by Snively et al. [8] at Purdue University in 1999. Several manufacturers of FT-IR spectrometers claim to have implemented continuous scan imaging for the first time, implying that they developed the idea. Perhaps they intended to say that they implemented it on their company s interferometer for the first time, but Lauterbach s group should be given credit for the original implementation. 

The SFC is a critical parameter for the fats and oils industry. The official American Oil Chemists Society (AOCS) wet method is dilatometery. Alternative wet methods are differential thermal analysis and differential scanning calorimetry (DSC). LR NMR was proved to be an alternative method for SFC determination in late 1950s. The early continuous wave LR NMR spectrometers rapidly found their way into the fats and oils industry, the method being accepted by the Instrumental Techniques Committee of the AOCS as early as in 1972. Presently the technical choice is radio frequency (RF) pulsed LR NMR. Pulse NMR spectrometers are more compact, very efficient, and relatively cheap. They have the advantage of exciting the protons in the whole sample at once. 

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