Patent ID: 7101467

Claim:
A method of extracting a charged species from a sample and concentrating it, comprising: providing an interconnected channel network comprising a first, second and third channel segment which intersect at a first fluid junction, the second channel segment terminating in a first fluid reservoir at one end and intersecting the first fluid junction at its other end, and a fourth channel segment intersecting the third channel segment at a second fluid junction at one end and terminating in a second fluid reservoir at its other end, the second fluid reservoir comprising a first buffer; flowing the charged species in the sample in a second buffer through the interconnected channel network by applying a first pressure differential across the first and second channel segments and a second pressure differential across the third and fourth channel segments, wherein the first pressure differential is larger than the second pressure differential and the first buffer has a different ionic strength than the second buffer; and applying a voltage differential across the first and second reservoirs which is sufficient to cause a substantial portion of the charged species in the sample in the first fluid junction to flow into the third channel segment.