Rhodamine B is a chemical compound and a dye

Dye

A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

. It is often used as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine dyes fluoresce

Fluorescence

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

 and can thus be detected easily and inexpensively with instruments called fluorometer

Fluorometer

A fluorometer or fluorimeter is a device used to measure parameters of fluorescence: its intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. These parameters are used to identify the presence and the amount of specific molecules in a medium...

s. Rhodamine dyes are used extensively in biotechnology applications such as fluorescence microscopy

Fluorescence microscope

A fluorescence microscope is an optical microscope used to study properties of organic or inorganic substances using the phenomena of fluorescence and phosphorescence instead of, or in addition to, reflection and absorption...

, flow cytometry

Flow cytometry

Flow cytometry is a technique for counting and examining microscopic particles, such as cells and chromosomes, by suspending them in a stream of fluid and passing them by an electronic detection apparatus. It allows simultaneous multiparametric analysis of the physical and/or chemical...

, fluorescence correlation spectroscopy

Fluorescence correlation spectroscopy

Fluorescence correlation spectroscopy is a correlation analysis of fluctuation of the fluorescence intensity. The analysis provides parameters of the physics under the fluctuations. One of the interesting applications of this is an analysis of the concentration fluctuations of fluorescent...

 and ELISA

ELISA

Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...

.

Rhodamine B is used in biology as a staining

Staining (biology)

Staining is an auxiliary technique used in microscopy to enhance contrast in the microscopic image. Stains and dyes are frequently used in biology and medicine to highlight structures in biological tissues for viewing, often with the aid of different microscopes...

 fluorescent dye, sometimes in combination with auramine O

Auramine O

Auramine O, also called Basic yellow 2, Pyocatanium aureum, aizen auramine, Pyoktanin Yellow, Canary Yellow, Pyoktanin, or C.I. 41000, is a diarylmethane dye used as a fluorescent stain. In its pure form, Auramine O appears as yellow needle crystals...

, as the auramine-rhodamine stain

Auramine-rhodamine stain

The auramine-rhodamine stain , also known as the Truant auramine-rhodamine stain, is a histological technique used to visualize acid-fast bacilli using fluorescence microscopy, notably species in the Mycobacterium genus. Acid-fast organisms display a reddish-yellow fluorescence. Although the...

 to demonstrate acid-fast

Acid-fast

Acid-fastness is a physical property of certain bacteria, specifically their resistance to decolorization by acids during staining procedures.Acid-fast organisms are difficult to characterize using standard microbiological techniques Acid-fastness is a physical property of certain bacteria,...

 organisms, notably Mycobacterium

Mycobacterium

Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. The genus includes pathogens known to cause serious diseases in mammals, including tuberculosis and leprosy...

.

Rhodamine B is tunable around 610 nm when used as a laser dye

Dye laser

A dye laser is a laser which uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths. The wide bandwidth makes them particularly suitable for tunable lasers and...

 . Its luminescence quantum yield

Quantum yield

The quantum yield of a radiation-induced process is the number of times that a defined event occurs per photon absorbed by the system. The "event" may represent a chemical reaction, for example the decomposition of a reactant molecule:...

 is 0.65 in basic ethanol

Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

, 0.49 in ethanol

Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

 , 1.0 , and 0.68 in 94% ethanol . The fluorescence yield is temperature dependent.

Solubility

The solubility of Rhodamine B in water is ~50 g/L. However, the solubility in acetic acid

Acetic acid

Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

 solution (30 vol.%) is ~400 g/L. Chlorinated tap water decomposes rhodamine B. Rhodamine B solutions adsorb to plastics and should be kept in glass .

Other uses

Rhodamine B is being tested for use as a biomarker

Biomarker (medicine)

In medicine, a biomarker is a term often used to refer to a protein measured in blood whose concentration reflects the severity or presence of some disease state...

 in oral rabies

Rabies

Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...

 vaccines for wildlife

Wildlife

Wildlife includes all non-domesticated plants, animals and other organisms. Domesticating wild plant and animal species for human benefit has occurred many times all over the planet, and has a major impact on the environment, both positive and negative....

, such as raccoons, to identify animals that have eaten a vaccine bait

Bait (luring substance)

Bait is any substance used to attract prey, e.g. in a mousetrap.-In Australia:Baiting in Australia refers to specific campaigns to control foxes, wild dogs and dingos by poisoning in areas where they are a problem...

. The rhodamine is incorporated into the animal's whiskers and teeth.

It is also often mixed with herbicides to show where they have been used.

Safety and health

In California, Rhodamine B is suspected to be carcinogenic and thus products containing it must contain a warning on its label.

In New Jersey, MSDS files state that there is limited evidence of carcinogenicity in laboratory animal, and no evidence at all in humans.