We developed a new experimental technique namedmagnetophoretic velocimetry to determine a small amountof paramagnetic species in a single microdroplet. Themagnetophoretic velocity of an aqueous droplet containingparamagnetic metal ion dispersed in an organic mediumcould response to a very small amount of the metal ionunder an inhomogeneous magnetic field. The paramagnetic droplet (2~8
m diam) used as a test sample in thisstudy was the aqueous droplet of manganese(II) chloridedispersed in ethylbenzoate whose density was nearly equalto water. A pair of small Nd-Fe-B magnets placed witha gap of 400
m generated an inhomogeneous magneticfield between the edges, at which the product of themagnetic flux density and the gradient,
B(
B/
x), was ashigh as 410 T
2 m
-1. When a silica capillary containingthe emulsion was inserted into the gap between themagnets, the magnetophoretic migration of the dropletswas observed with a video microscope. The magnetophoretic velocity divided by the squared radius of thedroplet was proportional to the MnCl
2 concentration inthe droplet, as predicted by a theoretical calculation. Theestimated detection limit in this simple method was lowerthan 10
-16 mol for manganese(II).