Mid-infrared microspectroscopy

R.T., Hanna, W.W. and Barton, F.B., II (1993) Mid-infrared microspectroscopy to assess lignin in plant tissues related to digestibility. Agron. J., 85,171-5. 

A. Hammiche, L. Bozec, M. J. German, J. M. Chalmers, N. J. Everall, G. Poulter, M. Reading, D. B. Grandy, F. L. Martin and H. M. Pollock, Mid-infrared microspectroscopy of difficult samples using near-held photo-thermal microspectroscopy. Spectroscopy, 2004, 19(2), 20. 

The other type of measurement that can be made with the microscope in its reflection mode is diffuse reflection (DR) spectroscopy. There are very few applications of mid-infrared microspectroscopy of neat samples because for mid-infrared DR spectrometry, samples should be diluted to a concentration of 0.5-5% with a nonabsorbing diluent, such as KBr powder, to preclude band saturation and severe distortion by reflection from the front surface of the particles. However, this mode has substantial application for NIR measurements, where sample dilution is not needed. Because absorption of NIR radiation by most samples is rather weak, they must be either at least 1mm thick or mounted on a reflective or diffusing substrate, such as a ceramic or Teflon disk. In the latter case, the spectrum is caused by a combination of DR, transflection, and front-surface reflection (with hopefully DR being the dominant process.)... 

The effective diameter of the beam from a synchrotron is typically about 100 pm and light is emitted into a narrow range of angles, making this an almost perfect radiation source for mid-infrared microspectroscopy. Not all synchtrotrons are equipped with infrared beam lines, but as the importance of the results that are being obtained continues to increase, this situation is changing. Beam time on... 

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