Sampling Considerations for FT-Raman Spectroscopy of Polymers and Solutions

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Abstract
The apparent absorption coefficient and optimal sample thickness for Fourier transform (FT)-Raman analysis of polyethylene, polyethylene terephthalate, cellulose, and cyclohexane were experimentally determined. With the use of these results, a relationship was developed that permits the optimal sample thickness for FT-Raman measurements to be determined by simply measuring the absorbance spectrum of a sample whose thickness is known. For samples with an apparent absorption coefficient of less than 0.08 cm−1, the sampling depth is limited by the depth of view of the instrument. For samples with an apparent absorption coefficient greater than 0.08 cm−1, the samples' optical and physical properties limit the sampling depth. The results are discussed in the context of scattering theory, sampling considerations, and spectral artifacts. Sampling considerations include the application of FT-Raman spectroscopy to the study of coated materials and layered structures.