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Ultraviolet-visible (UV-Vis) spectroscopy is a technique that identifies chemicals based on the interaction of molecules with electromagnetic radiation in the ultraviolet-visible region (10,000-33,333cm-1 or 300-1000 nm). Molecular absorbances of UV-Vis light cause electronic transitions within molecules. These transitions typically occur with the presence of a transition metal ion, or a conjugated organic molecule. Point analysis (“benchtop”) systems are used for analyzing liquid phase materials, although a few systems are also capable of analyzing gases and solids. UV-Vis instrumentation has been scaled down to hand-held size for specific colorimetric applications, but most research-grade instruments are of larger size, and are often combined with NIR instrumentation. There are UV-Vis reference databases, but there is much less specificity in a UV-Vis spectrum compared to MIR data, making it a secondary verification technique. UV-Vis is can only see four of the amino acids which have strong absorbances in this electromagnetic region (i.e., histidine, tyrosine, alanine and tryptophan). The absorbances themselves are not unique as many chemicals have the same conjugated moieties. The UV-Vis information is typically used in conjunction with another analytical technique to determine a specific biological sample.