Patent ID: 7858926

Claim:
An apparatus for analyzing chemical species, comprising: (a) an ion source for producing ions from a sample substance; (b) at least one vacuum stage having means for pumping away gas to produce a partial vacuum; (c) means for delivering said ions from said ion source into one of said at least one vacuum stage; (d) a collision cell configured in at least one of said at least one vacuum stage, said collision cell comprising an entrance end through which said ions may be directed into said collision cell; an exit end through which ions may exit said collision cell; and at least one higher neutral gas pressure region in which the neutral gas pressure is adjustable to be higher than in any other vacuum region proximal to said collision cell, such that collisions between said ions and neutral gas molecules occur within said at least one higher neutral gas pressure region while such collisions essentially do not occur within other vacuum regions proximal to said collision cell; (e) a detector configured in one of said at least one vacuum stage; (f) at least two multipole ion guide segments, each of said multipole ion guide segments having a plurality of poles, wherein at least a portion of each of said at least two multipole ion guide segments is positioned within said collision cell; and (g) independent RF frequency and DC voltage sources applied to each of said at least two multipole ion guide segments, wherein said RF frequency and DC voltages applied to each of said at least two multipole ion guide segments are controlled independently of each other.