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.