Shape of UV Absorption Curves

The solvent may affect the appearance of the spectrum, sometimes dramatically. Polar solvents generally wipe out the vibrational fine structure in a spectrum. Solvents may also shift the position of the absorption band, as will be discussed. For the visible region of the spectrum, any colorless solvent can be used in which the sample is soluble. 

The common solvents used in UV/VIS spectroscopy are listed in Table 5.5, along with their low-wavelength cutoff. At wavelengths shorter than the cutoff wavelength, the solvent absorbs too strongly to be used in a standard 1 cm sample cell. The cutoff is affected by the purity of the solvent. For spectroscopy, the solvents should be of spectral or spectrochemical grade, conforming to purity requirements set by the American Chemical Society. 

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