Ultraviolet-visible-near infrared spectroscopy (UV-Vis-NIR) refers to absorption or reflectance spectroscopy in the visible (400 – 700nm) and adjacent UV (200 – 400nm) and near-infrared (700 – 2500 nm) ranges of electromagnetic spectrum that causes many organic molecules to undergo electronic transitions.

The Beer-Lambert law states that the absorbance of a solution is directly proportional to the concentration of the absorbing species in the solution and the path length. Thus, for a fixed path length, UV-Vis-NIR spectroscopy can be used to determine the concentration of the absorber in a solution.

The wavelengths of absorption peaks can be correlated with the types of bonds in a given molecule and are valuable in determining the functional groups within a molecule.

UV-Vis-NIR spectroscopy is routinely used in analytical chemistry for the quantitative determination of different analytes, such as transition metal ions, highly conjugated organic compounds, and biological macromolecules. Spectroscopic analysis is commonly carried out in solutions but solids may also be studied.

(1) Determine concentrations of an absorbing species in solution in a quantitative way; the absorbing species can be transition metal ions, organic compounds, or biological macromolecules.

(2) Detect impurities in an organic liquid.

(3) Determine the kinetics or rate constant of a chemical reaction.

(4) Measure thickness and optical properties of thin film on a wafer.

(5) Applications of NIR spectroscopy include the analysis of foodstuffs, pharmaceuticals, combustion products, and a major branch of astronomical spectroscopy.

Wikipedia:  Ultraviolet–Visible Spectroscopy

Wikipedia:  Near-infrared Spectroscopy