Molecule of the Week: Rhodamine B

Rhodamine B  

Molecular Weight:	442.55

I use this dye to check electroosmotic flow (EOF) in microfluidic channels. EOF has to be  suppressed in the channels for many microfluidic experiments. Because of the charge developed on the surface of microfluidics channels buffer solution also moves when a voltage is applied. It moves from positive to negative electrode in glass microfluidic channel. RdB helps to monitor the EOF in the channel. Dye is injected into the positive electrode reservoir. Because it is a neutral dye any dye detected in the negative electrode side is due to EOF.
The solubility in water is ~50 g/l. However, the solubility in acetic acid 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 in oral rabies vaccines 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.

CAS Number:509-34-2


Formula: C₂₈H₃₀N₂O₃

IUPAC: 3',6'-Bbis(diethylamino)spiro[isobenzofuran-1(3h),9'-[9h]xanthene]-3-one

Rhodamine B, a neutral dye, is often used as a tracer to determine the rate and direction of flow and transport. This is fluorescent dye. It can thus be detected easily and inexpensively with instruments called fluorometers. Rhodamine dyes are used extensively in biotechnology applications such as fluorescence microscopy, flow cytometry, fluorescence correlation spectroscopy and ELISA.

Rhodamine B is used in biology as a staining fluorescent dye, sometimes in combination with auramine O, as the auramine-rhodamine stain to demonstrate acid-fast organisms, notably Mycobacterium.

Rhodamine B is tunable around 610 nm when used as a laser dye . Its luminescence quantum yield is 0.65 in basic ethanol, 0.49 in ethanol , and 0.68 in 94% ethanol. 

http://en.wikipedia.org/wiki/Rhodamine_B