A device for separating non-ions from ions is disclosed. The device includes a plurality of electrodes positioned around a center axis of the device and having apertures therein through which the ions are transmitted. An inner diameter of the apertures varies in length. At least a portion of the center axis between the electrodes is non-linear.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 The invention was made with Government support under Contract DE-AC05-76RL01830, awarded by the U.S. Department of Energy, and Grant No. R21 GM103497 awarded by the National Institutes of Health. The Government has certain rights in the invention.