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 a
fluorometer). 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. Other popular tracer dyes are
rhodamine,
pyranine and
sulforhodamine B.
Quantitative tracing Carbon sampling was the first method of technology-assisted dye tracing that was based on the absorption of dye in
charcoal. 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 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.
Tracing methods 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: • Resistance to absorption • Surface water loss • Limitations of use in acidic waters 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. ==Applications==