A method and apparatus are provided for obtaining a reproducible sample of solid particles. For the slot-dependent detection of the actuation of locking elements on the part of the base unit, it is proposed to arrange the arresting element such that, in the rest position, it is concealed by a movable covering in such a way that the arresting element is only accessible once the covering has been removed. After that, the control unit controls the inkjet head unit and the UVLED unit to move in the direction opposite to the scanning direction and controls the UVLED to emit ultraviolet light of a second light quantity.