Patent ID: 8637816

Claim:
A method for acquiring a mass spectrum, the method comprising: (a) accumulating a plurality of parent ions having a range of m/z ratios in an ion scanning trap; (b) ejecting parent ions of a selected first m/z ratio from the ion scanning trap into a collision cell, wherein other parent ions of different m/z ratios remain stored in the ion scanning trap during ejection of the selected parent ions; (c) producing fragment ions from at least some of the selected parent ions in the collision cell; (d) confining the selected parent ions and the fragment ions to an ion confinement region that converges from an ion acceptance aperture to an ion emission aperture of the collision cell, wherein the ion emission aperture is smaller than the ion acceptance aperture; (e) transmitting the fragment ions from the cell exit into a mass analyzer to acquire spectral data; and (h) repeating steps (b)-(e) one or more times for other parent ions accumulated in the ion scanning trap having one or more selected m/z ratios different from the first m/z ratio, wherein a plurality of fragment ion spectra are acquired from a corresponding plurality of parent ions of different respective m/z ratios.