Ultraviolet microscopy

UV microscopic techniques have become increasingly precise over the years. In the present section an outline will be presented of the type of information which can be obtained by UV microscopy, together with a discussion of experimental techniques and the limitations of the methods. 

Springer Series in Wood Science Methods in Lignin Chemistry (Edited by S.Y. Lin and C.W. Dence) 

The resolving power of a UV microscope is better than that of an optical microscope, but much lower than that of an electron microscope and is given by the expression 

UV microscopes are supplied mainly by two optical companies, Zeiss and Leitz, in the Federal Republic of Germany. The major difference between the Zeiss and the Leitz instruments lies in their optical systems. The Leitz microscope uses quartz refleeting objectives, while Zeiss uses quartz refractive objectives. Both objectives are achromatic for a wide portion of the UV and visible light range, with no shift in focus accompanying the change of wave- 

UVA light (320-400 nm) can cause reversible corneal damage on short exposure, while UVB (280-320 nm) or long exposure to UVA can produce cataracts and damage to the lens. It is most convenient to view UV microscope images with a small TV camera fitted with a UV sensitive vidicon tube. The samples of interest in UV microscopy absorb strongly in the UV but are usually transparent in the visible. In order that a UV absorbing compound may be seen in a sample it is necessary to remove that part of the spectral output of the lamp (usually visible) which is not absorbed by the sample. 

For many applications of the UV microscope it is necessary to make quantitative measurements of the concentration of UV absorber as a function of position within the field of view. BilUngham et 

Polymers containing UV stabilisers or fluorescent additives are an obvious target for UV microscopy, but the potential range of applications is much wider, in that UV absorbers or fluorescers can be selectively bound to specific chemical entities in the polymer or will preferentially interact with, or dissolve in, parts of the structure. A variety of applications of the UV microscope to studies of polymers has been reported (Table 5.15). Many applications of UV microscopy require quantitative analysis. 

Qualitative and quantitative measurements of polymers with a strongly UV absorbing or fluorescent component Distribution analysis of additives in polymers Additive concentration profiling Additive partitioning 

Determination of the diffusion rates of UV-absorbing or fluorescent additives in solid polymers Polymer oxidation studies Morphological and structural studies Contaminant analysis 

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B. J. Fergus, "The Distribution of Lignin in Wood as Determined by Ultraviolet Microscopy," Ph.D. thesis, McGill University, Montreal, Canada,... 

To visualize whether or not wood can be delignified by laccase III, ultraviolet photomicrographs (280nm) were taken before and after treatment of 0.5 mjLt cross-sections of red pine with laccase III (Figure 11). After enzyme treatment areas having an absorbance less than 0.2 in the secondary wall, and an absorbance less than 0.4 in the middle lamella, appeared. Each part of the secondary wall, middle lamella, and cell junction was subjected to ultraviolet microscopy, and absorption curves in the 240-300nm region were determined. The absorption curves of three samples after treatment... 

Jhe theoretical lower limit of resolution of the light microscope is about 0.2 micron—i.e., 2000 A. This figure can be reduced in favorable circumstances by using phase-contrast or interference microscopy. Ultraviolet microscopy of coal was attempted at the Division of Coal Research, but without success owing to the opacity of coal to ultraviolet radiation. Vigorous attempts are being made to develop x-ray microscopy, and its limit of resolution is already an order better than that of the light microscope. 

Musha Y, Goring DAI (1975) Distribution of synngyl and guaiacyl moieties in hardwoods as indicated by ultraviolet microscopy Wood Sci Technol 9 45-58 Nimz HH (1974) Beech lignin - proposal of a constitutional scheme Angew Chem Int Ed 13 313-321... 

Schuerch C (1952) The solvent properties of liquids and their relation to the solubility, swelling, isolation and fractionation of lignin J Am Chem Soc 74 5061-5067 Scott JAN, Procter AR, Fergus BJ, Goring DAI (1969) The application of ultraviolet microscopy to the distribution of lignin in wood Description and validity of the technique Wood Sci Technol 3 73 - 92... 

Fergus BJ, Goring DAI (1970) The distribution of lignin in birchwood as determined by ultraviolet microscopy Holzforschung 24 118-124 Fergus BJ, Procter AR, Scott JAN, Goring DAI (1969) The distribution of lignin in spruce wood as determined by ultraviolet microscopy Wood Sci Technol 3 117-138... 

Scott JAN, Goring DAI (1970b) Photolysis of wood microsections in the ultraviolet microscopy Wood Sci Technol 4 237-239... 

Wood JR, Goring DAI (1973) Ultraviolet microscopy at wavelengths below 240nm J Microscopy 100 105-111... 

Fergus BJ, Goring DAI (1970b) The distribution of lignin in sprucewood as determined by ultraviolet microscopy Holzforschung 24 118-124... 

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