• In this method, a spectrophotometer emits a broad spectrum of UV and visible light through a sample, and the intensity of transmitted or absorbed light is measured by a detector.
• The Beer-Lambert law is commonly used to relate the absorbance of light by a sample to its concentration and the path length of the light through the sample.
• UV-Vis spectrophotometry is widely used in biochemistry for analyzing nucleic acids, proteins, and other biomolecules, as well as in chemical analysis for determining the concentration of various compounds.

Infrared (IR) Spectrophotometry:
• Infrared spectrophotometry measures the absorption of infrared radiation by a substance.
• This method is based on the principle that molecules absorb infrared radiation at specific wavelengths corresponding to the vibrational and rotational modes of the chemical bonds within the molecule.
• IR spectrophotometry is used for structural analysis, identification of functional groups, and qualitative and quantitative analysis of organic and inorganic compounds.

Spectrophotometers are equipped with monochromators or filters to select specific wavelengths of light for analysis. The choice of wavelength depends on the nature of the sample and the information sought. For example:

UV-Visible Wavelengths:
• UV region: Typically ranges from 200 to 400 nm. Common applications include DNA and protein analysis, enzymatic assays, and measurement of organic compounds.
• Visible region: Ranges from 400 to 800 nm. Used for colorimetric assays, analysis of pigments, and determination of metal ions.