Infrared microspectrophotometry

Most of the techniques employed in fibre analysis are nondestructive tests to determine whether the fibre is natural (obtained from animal, plant, or mineral) or synthetic (wholly manufactured from chemicals or regenerated from natural fibres) and the fibre type (e.g., determining if the fibre is wool, cotton, nylon, polyester, etc.). Whether any chemical treatments have been carried out (such as bleaching or the use of delustrants) is noted and the colour is also determined. Many of the techniques commonly used in these analyses include low- and high-power microscopes, Fourier transform infrared (FTIR) microscopy, polarising Ught microscopy, fluorescence microscopy, and microspectrophotometry (MSP). 

Other useful microscopic analytical techniques include hot stage, fluorescence, and cathodolumines-cence microscopies micro-infrared spectroscopy micro-Raman spectroscopy ultraviolet-visible microspectrophotometry and X-ray diffraction however, the discussion of these techniques is beyond the scope of this article. Briefly stated, each of these techniques can be used to ascertain additional information about characteristic properties of a material. The microscopist must be aware of all of these techniques, and others, so as to be able to extract the necessary information from a sample when the need arises. 

Ultraviolet/Visible Microspectrophotometry. Infrared spectroscopy and ultraviolet/visible microspectrophotometry are both based on the principle of the interaction of radiation with a sample. However, ultraviolet/visible microspectrophotometry is typically used to compare the dye or pigment composition of samples. The technique is used to determine the color of a sample and identify subtle differences in color that cannot be seen with the naked eye. 

The only way to overcome all of these problems is to use a nondestructive in situ analytical technique. Given the small quantities of colorants present in trace samples, ultaviolet (UV)-visible microspectrophotometry is one of the few analytical techniques that can be used in situ. Unfortunately, the electronic spectra data obtained provide only a very limited amount of molecular information to compare samples and help in the identification of a dye. The technique is very poor where discrimination of dyes in the mixture is required and this can be a key piece of information, for example, if a fiber is to be related to a garment. Thus, Raman spectroscopy using near-infrared excitation and SERRS are techniques with very considerable potential in forensic analysis. 

Merging of spectroscopy with microscopy has generated an entirely new discipline, termed microspectroscopy, which allows measurement of the spatial distribution of chemical stractures in materials. Microspectrophotometry (MSP), primarily in the UVAHS and NIR ranges (220 to 2500 nm), has been practised in some way since the 1930s with emphasis on the microscope functionality [368, 369]. On the other hand, the recent convergence of infrared with microscopy accentuates the spectroscopic functionality. Microspectroscopy is a powerful tool for characterisation of micro samples, for examination of heterogeneous materials and for analysis of processes such as migration that involve spatial... 

---