UV-Vis Spectrophotometer


Ultraviolet-visible spectroscopy or ultraviolet-visible spectrophotometry (UV-Vis or UV/Vis) refers to absorption spectroscopy in the ultraviolet-visible spectral region. This means it uses light in the visible and adjacent (near-UV and near-infrared (NIR)) ranges. UV/Vis spectrophotometer is used in the quantitative determination of concentrations of the absorber in the solutions of transition metal ions and highly conjugated organic compounds. The UV-Vis Spectrophotometer (Varian Cary 100) (Figure 1) was established in the Core Lab in the Core Lab (201D) in 2007 with the DRDO grant of the Institute.

Basic Principle:

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 (Figure 2). Thus, for a fixed path length, UV/Vis spectroscopy can be used to determine the concentration of the absorber in a solution. The absorbance changes with concentration. This can be taken from references (tables of molar extinction coefficients), or more accurately, determined from a calibration curve.

Unique Features:

Quartz overcoating protects the optics from the environment and allows cleaning without damage to their reflective surface. Sealed optics prevents exposure to corrosive environments. Double choppers ensure that the sample and reference beam strike the detector at the same point, removing any errors due to non uniformity of the detector. Variable slits allow optimum control over data resolution. The spectral bandwidth can be set down to 0.2 nm. A phase locked wavelength drive prevents peak shifts and peak suppression at high scan speeds. The large sample compartment gives more flexibility in sample size.


Department of Chemical Engineering,NL Lab,
IIT Kanpur


Prof. Nishith Verma

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Figure 1

Figure 2

Figure 3