Patent ID: 7531793
Filing Date: 2009-05-12
Classification: H01J

Abstract:
1. A tandem mass spectrometry system comprising: a first mass spectrometer for ionizing a sample to create ionized precursor ions and for separating and extracting the ionized precursor ions; deceleration means for decelerating the precursor ions which have been separated and extracted by the first mass spectrometer; and a second mass spectrometer for mass analyzing the product ions that are constituent materials of the precursor ions; said deceleration means having a decelerating electrode arrangement and a variable power supply for varying a voltage applied to the decelerating electrode arrangement that produces a decelerating electric field in a direction of deceleration intersecting at a small angle with a direction of motion of the precursor ions ejected from the first mass spectrometer; said decelerating electrode arrangement having first, second, and third electrodes arranged in an opposite relationship to each other in the direction of deceleration from a position close to an exit port of the first mass spectrometer from which the precursor ions are ejected; said decelerating electrode arrangement further including a fourth electrode spaced in a direction perpendicular to the direction of deceleration from a midpoint between the second and third electrodes in the direction of deceleration; said midpoint being set to a position where velocity components of the precursor ions in the direction of deceleration are null; and said variable power supply acting (i) to place the second and third electrodes at the same potential when the precursor ions arrive at the midpoint, (ii) to place the fourth electrode at a lower potential than the second and third electrodes in a case where the precursor ions are positively charged, and (iii) to place the fourth electrode at a higher potential than the second and third electrodes in a case where the precursor ions are negatively charged.