Rhodamine B/ˈroʊdəmiːn/ is a chemical compound and a dye. It is often used as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with fluorometers.
Rhodamine B is often mixed with herbicides to show where they have been used.
It is also being tested for use as a biomarker in oral rabiesvaccines for wildlife, such as raccoons, to identify animals that have eaten a vaccine bait. The rhodamine is incorporated into the animal's whiskers and teeth. Rhodamine B is an important hydrophilic xanthene dye well known for its stability and is widely used in the textile industry, leather, paper printing, paint, coloured glass and plastic industries.
Rhodamine B (BV10) is mixed with quinacridone magenta (PR122) to make the bright pink watercolor known as Opera Rose.
Properties
Rhodamine B closed form (A) and open form (B)
Rhodamine B can exist in equilibrium between two forms: an "open"/fluorescent form and a "closed"/nonfluorescent spirolactone form. The "open" form dominates in acidic condition while the "closed" form is colorless in basic condition.
A small amount of aqueous Rhodamine B in a 250 mL bottle
The fluorescence intensity of rhodamine B will decrease as temperature increases.
The solubility of rhodamine B in water varies by manufacturer, and has been reported as 8 g/L and ~15g/L, while solubility in alcohol (presumably ethanol) has been reported as 15g/L. Chlorinated tap water decomposes rhodamine B. Rhodamine B solutions adsorb to plastics and should be kept in glass.
Rhodamine B is tunable around 610nm when used as a laser dye. Its luminescence quantum yield is 0.65 in basic ethanol, 0.49 in ethanol, 1.0, and 0.68 in 94% ethanol. The fluorescence yield is temperature dependent; the compound is fluxional in that its excitability is in thermal equilibrium at room temperature.
Safety and health
In California, rhodamine B is suspected to be carcinogenic and thus products containing it must contain a warning on its label. Cases of economically motivated adulteration, where it has been illegally used to impart a red color to chili powder, have come to the attention of food safety regulators.
↑Cai SS, Stark JD (November 1997). "Evaluation of five fluorescent dyes and triethyl phosphate as atmospheric tracers of agricultural sprays". Journal of Environmental Science and Health, Part B. 32 (6): 969–83. Bibcode:1997JESHB..32..969C. doi:10.1080/03601239709373123.
↑Casey KG, Quitevis EL (1988). "Effect of solvent polarity on nonradiative processes in xanthene dyes: Rhodamine B in normal alcohols". The Journal of Physical Chemistry. 92 (23): 6590–6594. doi:10.1021/j100334a023.
↑Kellogg RE, Bennett RG (1964). "Radiationless Intermolecular Energy Transfer. III. Determination of Phosphorescence Efficiencies". The Journal of Chemical Physics. 41 (10): 3042–3045. Bibcode:1964JChPh..41.3042K. doi:10.1063/1.1725672.
↑Snare M (1982). "The photophysics of rhodamine B". Journal of Photochemistry. 18 (4): 335–346. doi:10.1016/0047-2670(82)87023-8.
↑Karstens T, Kobs K (1980). "Rhodamine B and rhodamine 101 as reference substances for fluorescence quantum yield measurements". The Journal of Physical Chemistry. 84 (14): 1871–1872. doi:10.1021/j100451a030.
12Ellis RC (November 16, 2015). "Reagent and Dye Solubility Chart". IHCWorld. Archived from the original on 30 January 2020. Retrieved 9 February 2020. This is to be used as a guide only as solubility data varies between manufacturers for the same product, especially for dyes. Note that most sources simply indicate that the compound is water soluble without providing a g/L value.