Rhodamine B is a chemical compound and a

dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...

. It is often used as a

tracer dye Dye tracing is a method of tracking and tracing various flows 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 qu ...

within water to determine the rate and direction of flow and transport. Rhodamine dyes

fluoresce Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...

and can thus be detected easily and inexpensively with

fluorometer A fluorometer, fluorimeter or fluormeter is a device used to measure parameters of visible spectrum fluorescence: its intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. These parameters ar ...

s. Rhodamine B is used in biology as a

staining Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissues), in cytology (microscopic study of cells), and in the ...

fluorescent dye, sometimes in combination with

auramine O Auramine O is a diarylmethane dye used as a fluorescent stain. In its pure form, Auramine O appears as yellow needle crystals. It is insoluble in water and soluble in ethanol and DMSO. Auramine O can be used to stain acid-fast bacteria (e.g. ' ...

, as the auramine-rhodamine stain to demonstrate

acid-fast Acid-fastness is a physical property of certain bacterial and eukaryotic cells, as well as some sub-cellular structures, specifically their resistance to decolorization by acids during laboratory staining procedures. Once stained as part of a sam ...

organisms, notably ''

Mycobacterium ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis ('' M. tuberculosis'') and ...

''. Rhodamine dyes are also used extensively in biotechnology applications such as

fluorescence microscopy A fluorescence microscope is an optical microscope that uses fluorescence instead of, or in addition to, scattering, reflection, and attenuation or absorption, to study the properties of organic or inorganic substances. "Fluorescence microsc ...

flow cytometry Flow cytometry (FC) is a technique used to detect and measure physical and chemical characteristics of a population of cells or particles. In this process, a sample containing cells or particles is suspended in a fluid and injected into the flo ...

fluorescence correlation spectroscopy Fluorescence correlation spectroscopy (FCS) is a statistical analysis, via time correlation, of stationary fluctuations of the fluorescence intensity. Its theoretical underpinning originated from L. Onsager's regression hypothesis. The analysis p ...

and

ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...

. It is also used in rose milk, a popular Indian beverage.

Other uses

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 biomedical contexts, a biomarker, or biological marker, is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, ...

in oral

rabies Rabies is a viral disease that causes encephalitis in humans and other mammals. Early symptoms can include fever and tingling at the site of exposure. These symptoms are followed by one or more of the following symptoms: nausea, vomiting, vi ...

vaccines A vaccine is a biological preparation that provides active acquired immunity The adaptive immune system, also known as the acquired immune system, is a subsystem of the immune system that is composed of specialized, systemic cells and pro ...

for

wildlife Wildlife refers to domestication, undomesticated animal species (biology), species, but has come to include all organisms that grow or live wilderness, wild in an area without being species, introduced by humans. Wildlife was also synonymous ...

, such as

raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the common raccoon to distinguish it from other species, is a mammal native to North America. It is the largest of the procyonid family, having a body length of , and a body weight of ...

s, to identify animals that have eaten a vaccine bait. The rhodamine is incorporated into the animal's

whiskers Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to touch, sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are c ...

and

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

. Rhodamine B (BV10) is mixed with quinacridone magenta (PR122) to make the bright pink watercolor known as Opera Rose.

Properties

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. 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 ~15 g/L, while solubility in alcohol (presumably

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...

) has been reported as 15 g/L. Chlorinated tap water decomposes rhodamine B. Rhodamine B solutions adsorb to plastics and should be kept in glass. Rhodamine B is tunable around 610 nm when used as a

laser dye Laser dyes are dyes used as laser medium in a dye laser. Laser dyes include the coumarins and the rhodamines. Coumarin dyes emit in the green region of the spectrum, whereas rhodamine dyes are used for emission in the yellow-red. The color emi ...

. Its luminescence

quantum yield The quantum yield (Φ) of a radiation-induced process is the number of times a specific event occurs per photon absorbed by the system. Applications Fluorescence spectroscopy The fluorescence quantum yield is defined as the ratio of the numb ...

is 0.65 in basic

, 0.49 in ethanol, 1.0, and 0.68 in 94% ethanol. The fluorescence yield is temperature dependent; the compound is

fluxional In chemistry and molecular physics, fluxional (or non-rigid) molecules are molecules that undergo dynamics such that some or all of their atoms interchange between symmetry-equivalent positions. Because virtually all molecules are fluxional in so ...

in that its excitability is in

thermal equilibrium Two physical systems are in thermal equilibrium if there is no net flow of thermal energy between them when they are connected by a path permeable to heat. Thermal equilibrium obeys the zeroth law of thermodynamics. A system is said to be in ...

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 Food defense is the protection of food products from ''intentional'' contamination or adulteration by biological, chemical, physical, or radiological agents introduced for the purpose of causing harm. It addresses additional concerns including phys ...

, where it has been illegally used to impart a red color to

chili powder Chili powder (also spelled chile, chilli, or, alternatively, powdered chili) is the dried, pulverized fruit of one or more varieties of chili pepper, sometimes with the addition of other spices (in which case it is also sometimes known as chili p ...

, have come to the attention of food safety regulators.

References

Notes

{{Stains Microscopy Microbiology techniques Laboratory techniques Histopathology Histotechnology Staining dyes Staining * Laser gain media Benzoic acids Aromatic amines Chlorides Quaternary ammonium compounds Triarylmethane dyes Xanthenes Diethylamino compounds Fluorescent dyes

Other uses

Properties

Safety and health

See also

References

Notes