Abstract: The sample crucibles inserted in a slide rod are introduced, through a high vaccum lock, into the ion source of a mass spectrometer. The slide rod, together with its drive, is mounted on a lock carriage which runs parallel to the direction of travel of the slide rod. The lock carriage has a separate drive and carries, on the end face which points towards the mass spectrometer, a stuffing box for the vacuum-tight passage of the slide rod. On the rear wall of the high vacuum lock is mounted an O-ring seal, which, with the lock carriage moved in, seals the remaining space between the rear wall of the lock and the end face of the lock carriage, in the region of the slide rod. The sample crucibles can be taken out selectively from the sample magazine, which can slide at right angles to the slide rod, by means of the holder mounted at the end of the slide rod.