UV-VIS spectroscopy

Introduction to UV-VIS

UV-VIS spectroscopy is routinely used in analytical chemistry for the quantitative determination of different analytes in solution. In Particle Analytical, concentration determinations by UV-VIS spectroscopy is used for solubility and dissolution/IDR measurements.

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Instrument and measuring principles

UV-VIS is used in analytical chemistry for the quantitative determination of different analytes containing π-electrons or non-bonding electrons (n-electrons), These bonds  absorb the energy in the form of ultraviolet or visible light to excite these electrons to higher anti-bonding molecular orbitals.

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 spectroscopy can be used to determine the concentration of the absorber in a solution. It is necessary to know the absorbance changes with concentration. For well-known samples this can be taken from references (tables of molar extinction coefficients), or more accurately, determined from a calibration curve.