Dye tracing is a method of tracking and tracing variousflows usingdye as aflow tracer when added to aliquid. 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.
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Fluorescent dyes are often used in situations where there is insufficient lighting (e.g., sewers or cave waters), and where precise quantitative data are required (measured by afluorometer).
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.[1]
Other popular tracer dyes arerhodamine,pyranine andsulforhodamine B.
Carbon sampling was the first method of technology-assisted dye tracing that was based on the absorption of dye incharcoal. Charcoal packets may be placed along the expected route of the flow, later the collected dye may be chemically extracted and its amount subjectively evaluated.
Filter fluorometers were the first devices that could detect dye concentrations beyondhuman eye sensitivity.
Spectrofluorometers, developed in the mid-1980s, made it possible to perform advanced analysis of fluorescence.
Filter fluorometers andspectrofluorometers 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 sampling area is analysed by a quantitative instrument to test the background fluorescence.
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.
Typical applications ofwater flow tracing include:[2]
Dye tracing may be used for the analysis ofblood circulation within various parts of the human or animal body. For example,fluorescent angiography, a technique of analysis of circulation inretina is used for diagnosing various eye diseases.
With modern fluorometers, capable of tracking single fluorescent molecules, it is possible to track migrations of single cellstagged by a fluorescent molecule (seefluorescein in biological research). For example, thefluorescent-activated cell sorting inflow cytometry makes it possible to sort out the cells with attached fluorescent molecules from a flow.