| 摘要 |
Mass spectrometer collision/reaction cell multipole (80) and method. The multipole may have first and second portions (82, 90) and an intermediate portion (86) therebetween, the first and second portions operating at first and second q values lower than a third q value at the intermediate portion. A low-mass cut-off of the multipole may be controlled by varying a q value from a first to at least a second value. The multipole may have multipole electrodes (80) disposed about a central axis and having a respective first portion, second portion, and intermediate portion therebetween which is radially closer to the central axis. Generally, the q value changes from a first relatively low value at the entrance end (20) to at least a second relatively higher value. This offers relatively high acceptance and ion transmission, while providing low-mass cut-off for removing undesired/interfering ions and helping reduce background count. Advantageously, there is a further change in q value downstream, to a third, relatively low value at the exit end (30), preferably the same as the first q value. |
