Functional groups, determination spectrophotometry

UV/VIS spectrophotometry can be used to determine many physico-chemical characteristics of compounds and thus can provide information as to the identity of a particular compound. Although UV/VIS spectra do not enable absolute identification of an unknown, they are frequently used to confirm the identity of a substance through comparison of the measured spectrum with a reference spectrum. However, UV spectrophotometry is not highly specific, and can obviously only be applied to polymer additives which are absorbers of UV radiation, i.e. contain chromophoric groups. Both UV and IR monitor functional entities rather than the entire molecular structure. A functional group s proximity to other electropositive or electronegative structures in a molecule affects the absorbance spectrum, allowing one to infer some details of molecular structure. 

Direct spectrophotometry in the visible and UV region has been used to determine low concentrations of functional groups in the surface of polymer films. Kato [56] followed the regeneration of carbonyl groups from 2,4-dinitrophenylhydrazones formed on the surface of irradiated polystyrene films by absorption measurements at 378 nm. 

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