Patent ID: 6753523
Filing Date: 2004-06-22
Classification: H01J

Abstract:
An apparatus for analyzing chemical species, comprising:(a) an ion source for operation at substantially atmospheric pressure to produce ions from a sample substance; (b) at least two vacuum stages, each of said vacuum stages having means for pumping away gas to produce a partial vacuum, the first vacuum stage comprising a vacuum pressure such that said ions produce by said ion source can move out of said ion source and into said first vacuum stage, said at least two vacuum stages being in communication with each other such that said ions can move through a sequence of said at least two vacuum stages; (c) a mass analyzer and detector located in at least one of said vacuum stages; (d) a multipole ion guide having at least two segments, each segment having a plurality of poles, respectively; (e) RF frequency and DC voltage sources applied to each of said at least two segments; (f) wherein at least a second one of said at least two segments of said multipole ion guide is configured for ion mass to charge selection of said ions and is located in one of said vacuum stages, and wherein the vacuum stage in which said at least a second one of said at least two segments is located in has a background pressure of at least 1Ã—10âˆ’2 torr, sufficiently high such that ions traversing the length of said at least a second one of said at least two segments will encounter collisions with neutral background gas; and (g) wherein said RF frequency and DC voltages applied to each of said at least two segments are controlled independently of each other.