A single or multiwell plate using membrane, preferably an ultrafiltration
membrane to filter selected solutes from a liquid is disclosed. In
particular, a preferred construction and method of sealing the membrane to
the interior of the well so as to form an integral seal between the top
portion of the well and the bottom portion is disclosed. The preferred
method is to use a heat seal device which secures the filter to the
underdrain portion of the device.
