ac010418v_si_001.pdf (47.33 kB)
Magnetophoretic Velocimetry of Manganese(II) in a Single Emulsion Droplet at the Femtomole Level
journal contribution
posted on 2001-09-28, 00:00 authored by Masayori Suwa, Hitoshi WataraiWe developed a new experimental technique named
magnetophoretic velocimetry to determine a small amount
of paramagnetic species in a single microdroplet. The
magnetophoretic velocity of an aqueous droplet containing
paramagnetic metal ion dispersed in an organic medium
could response to a very small amount of the metal ion
under an inhomogeneous magnetic field. The paramagnetic droplet (2∼8 μm diam) used as a test sample in this
study was the aqueous droplet of manganese(II) chloride
dispersed in ethylbenzoate whose density was nearly equal
to water. A pair of small Nd−Fe−B magnets placed with
a gap of 400 μm generated an inhomogeneous magnetic
field between the edges, at which the product of the
magnetic flux density and the gradient, B(∂B/∂x), was as
high as 410 T2 m-1. When a silica capillary containing
the emulsion was inserted into the gap between the
magnets, the magnetophoretic migration of the droplets
was observed with a video microscope. The magnetophoretic velocity divided by the squared radius of the
droplet was proportional to the MnCl2 concentration in
the droplet, as predicted by a theoretical calculation. The
estimated detection limit in this simple method was lower
than 10-16 mol for manganese(II).