Raman microspectrophotometry

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. 

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. 

The UV-vis transmittance spectrum shown in Figure 6 contains a Soret band at 406 nm and Q-bands at 510, 538, 580, and 644 nm, the latter being especially characteristic of hemin aggregates as determined by photoacoustic spectroscopy (34) and microspectrophotometry (35). Given the number and energies of iht bands in the absorption spectrum there exist manifold possibilities for resonance Raman enhancement studies. 

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