What is isosbestic point?

An isosbestic point is a specific wavelength or point in a spectrum where the absorbance of a sample does not change during a chemical reaction or physical process. This means that at the isosbestic point, the concentrations of different species absorbing at that wavelength are changing in equal proportions, resulting in a constant absorbance value. Isosbestic points are often used in spectroscopic analysis to monitor chemical reactions, identify different species, or quantify the concentration of a particular analyte in a sample. The presence of an isosbestic point can indicate that the reaction is following a simple stoichiometry or that the reaction is reversible.