A magnetic adjustment mechanism 100 comprising a chamber 10, an element 12 pivotally mounted within the chamber 10 and comprising a magnetic portion 14, and a magnetic actuator 18 arranged outside the chamber 10 to allow magnetic coupling with the magnetic portion 14 of the element 12 such that movement of the magnetic actuator 18 causes an adjustment of the position of the element 12. The adjustment mechanism 100 may be used within a vacuum chamber of a mass spectrometer to control the position of a moveable element from outside the chamber.