Attenuated total reflection (ATR) infrared microscopy has been investigated for use in the microanalysis of the surface of organic materials, such as plastic, rubber and paint. A unique ATR unit, consisting of an ATR prism and a sample holder, is has been designed to achieve ATR measurements using a conventional infrared microscope. The prism, made from zinc selenide, has the shape of apillar with a hexagonal cross-section. The prism comprises four totally reflecting surfaces including a sample-contacted surface on which an infrared beam is focused. The reflecting surfaces are oriented so that the optical axis of the incident beam way agree well with that of the outgoing beam even if the measured point of interest is shifted on the sample surface. Consequently, this ATR infrared microspectroscopic technique enables not only a point analysis but line and area analysis. The fundamental performances of the ATR technique are as follows: The minimum measurement size in the point analysis is about 10 mm square. The precision of absorption intensity and the resolution in the line analysis are 1.0% in the coefficient of variation and 20 mm in length, respectively. The effective dimensions for the area analysis are 1.3 mm by 6.6 mm. Furthermore, the availability of this ATR system was confirmed from some applications to the microanalysis of organic materials and products.

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