Apparatus (1) for withdrawing respective liquid samples from vials (2) which are closed by closure caps (4) includes a plurality of racks (7) for accommodating the vials (2). A device (10) including a housing (25) is slideably carried on a gantry (9) which in turn is slideably carried on guide tracks (12) to provide two degrees of movement of the device (10) for selective alignment of the device (10) with the vials (2). An abutment member (43) is driven vertically by a second gearwheel (51) by a drive shaft (27) through a first gearwheel (40) and a dog clutch (52). A cannula which is secured within a first gear rack (33) is driven vertically by the first gearwheel (40). On engagement of the abutment member (43) with the closure cap (4) of the selected vial (2), the clutch (52) decouples the second gearwheel (51) from the first gearwheel (40) so that the cannula (28) is urgeable through the closure cap (4) into the vial (2).