UV-Visible (UV-Vis) Spectroscopy

Ultraviolet-visible spectroscopy measures the absorption of light in the 200–800 nanometre range arising from electronic transitions within a molecule's...

Ultraviolet-visible spectroscopy measures the absorption of light in the 200–800 nanometre range arising from electronic transitions within a molecule's chromophoric system, most commonly involving conjugated pi-electron systems and lone-pair-bearing heteroatoms. The wavelength of maximum absorption, λmax, together with the molar extinction coefficient, provides preliminary information about the extent of molecular conjugation and, for compounds bearing an extended chromophore, can offer an early indication of successful synthesis or structural modification through observed shifts in absorption maxima. Although UV-Vis spectroscopy alone rarely provides sufficient structural detail for unambiguous compound identification, it remains a rapid, inexpensive, first-line confirmatory technique and additionally underlies UV detection in the chromatographic purity and quantification methods addressed in Phase 4 of this text.