5 n7 An analyzer is described comprising a device (1) for scanning containers (4) filled with body fluid (9) and held in a tray (5), the openings of which are sealed by means of a sealing member (8), e.g. a stopper (81) or cup (84). The opto-electronic scanning device (1) consists of a receiver (2) and a transmitter (3) comprising a plurality of vertically arranged receiver elements (6) and transmitter elements (7), respectively, facing each other in a registered manner. Receiver (2) and transmitter (3) are arranged on a pivotable transport path (12) for the containers (4) between an input station (20) and two processing stations (24, 25). During the transport of container (4) through the scanning device (1), the intensity of the scanning beam (14) of the transmitter elements (7) can be controlled from a low to a high level by means of a control unit (40) comprising a microprocessor (43). Shape and/or size of the sealing member (8) is thereby detected by means of the low intensity (50) and transmittance or type of the sealing member (8) by means of the high intensity (51). In this way, the transport direction of the containers (4) can be controlled such that a container (4) having a stopper (81) is moved to an opening means (26) and a container (4) with or without a cup (84) is moved to an aspirator (27) for body fluids (9).