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Fluorescein is a fluorescent dye which is used in a number of different applications in the sciences and medicine. In pure state, fluorescein is a red or orange powder which is dissolved in alkaline solutions to make up a yellow solution which will glow green. In addition to using straight fluorescein, researchers also work with various derivatives of the compound which are designed to conjugate to specific types of molecules and perform other functions.
In medicine, this compound has a broad range of uses. Ophthalmologists use it in eye exams, staining the eye with the dye to look for signs of tears in the cornea, and they can also use it for fluorescein angiography of the retina, using the dye to look for leaks inside the blood vessels in the eye. The chemical can also be used as a tracer in other areas of the body, and it is utilized in microscopy and as a stain. In addition, fluorescein derivatives are used in the lab to identify compounds in fluid samples, with the chemical attaching to specific proteins to act as a flag.
In laboratory science, fluorescein can be used for protein labeling, and in a number of other tasks. Outside the lab, this dye was historically used to trace river flow and flows of pollutants, although it has been replaced in some regions due to concerns about the environmental impact of these practices. This compound is also used in dye lasers and some other scientific instruments which need to be able to fluoresce.
Oceanographers and hydrologists have historically used fluorescein to trace the flow of currents through bodies of water of interest. In this case, a load known as the “point source” is released in a set location and followed as it moves through the water. In addition to providing data about current flow, the movement of the fluorescein can also be used to trace contaminants, by tagging the contaminant with the compound and watching to see where it goes. This information can be used in environmental cleanup efforts.
Several chemical companies manufacture fluorescein and derivatives of this compound, such as fluorescein isothiocyanate. These companies can sell the product packaged as powder or solution, in various sizes to meet the needs of users. This compound is one of the most widely used fluorescing molecules, and numerous photographs featuring this chemical compound in action can be found on scientific websites.