Ultraviolet-visible (UV-vis) spectroscopy is used to obtain the absorbance spectra of a compound in solution or in the solid state. The instrument detects the absorbance of light energy or electromagnetic radiation, which excites electrons of the analyzed compound from the ground state to the first singlet excited state. The UV-vis region of energy for the electromagnetic spectrum ranges from 1.4 to 6.3 eV which corresponds to the range of wavelengths from 900 to 200 nm. UV-vis spectral data can be used as a source of information for both, qualitative and quantitative analysis of the studied compounds or molecules. UV-vis spectroscopy works well on samples in a liquid phase or solutions. Limitations can be identified in the analysis of highly concentrated solutions or even suspended solid particles, where the light scattering can occur, which negatively affects the measured spectra.