Calcein Blue is a blue-fluorescent, short-term dye.

Calcein blue AM is only weakly fluorescent (excitation/emission maxima 322/435 nm). Upon cleavage of the AM esters by intracellular esterases, this tracer becomes relatively polar and is retained by cells for several hours. In addition, its fluorescence intensity increases, and its fluorescence spectra shift to longer wavelengths, with excitation/emission maxima of 360/449 nm [1]. When dopamine is added to a solution of the calcein blue–Fe2 complex, dopamine–Fe2 complex is formed as the result of a ligand exchange reaction between calcein blue and dopamine which permits the fluorescence from calcein blue to be recovered. The fluorescence intensity at the wavelength of 440 nm (at the excitation wavelength of 340 nm) is found to be proportional to the concentration of the dopamine added to the calcein blue–Fe2 complex solution, which permits dopamine to be quantitatively determined [2].