Dye tracing is a method of tracking and tracing various Fluid dynamics using dye as a flow tracer when added to a liquid. Dye tracing may be used to analyse the flow of the liquid or the transport of objects within the liquid. Dye tracking may be either qualitative, showing the presence of a particular flow, or quantitative, when the amount of the traced dye is measured by special instruments.
In 1871, fluorescein was among the first fluorescent dyes to be developed. Its disodium salt (under the trademark "uranine") was developed several years later and still remains among the best tracer dyes. An educational website about karst and dye tracing, by Crawford Hydrology Laboratory / Center for Cave and Karst Study in association with Western Kentucky University
Other popular tracer dyes are rhodamine, pyranine and sulforhodamine B.
Filter fluorometers were the first devices that could detect dye concentrations beyond human eye sensitivity.
Spectrofluorometers, developed in the mid-1980s, made it possible to perform advanced analysis of fluorescence.
Filter fluorometers and spectrofluorometers identify the intensity of fluorescence that is present in a liquid sample. Different dyes and chemicals produce a distinctive wavelength that is determined during analysis.
Each different type of dye has significant performance factors that distinguish them in different environments. These performance factors include:
Depending on the environment, water flows possess certain factors that can affect how a dye performs. Natural fluorescence in a water flow can interfere with certain dyes. The presence of organic material, other chemicals, and sunlight can affect the intensity of dyes.
With modern fluorometers, capable of tracking single fluorescent molecules, it is possible to track migrations of single cells fluorescent tag (see fluorescein in biological research). For example, the fluorescent-activated cell sorting in flow cytometry makes it possible to sort out the cells with attached fluorescent molecules from a flow.
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