The sample injection cell (24) comprises a body (27) and a bore (23) through the body for receiving a probe (20) to pass fluid sample into the bore. A transverse passageway (28) into the body permits a diluent to enter the bore and be mixed with a sample in a predetermined ratio and be dispensed directly into the flow cell (33). The diluent simultaneously washes the probe when the probe is located in the bore. A waste basin (47) forms part of an integral unit and is adjacent the bore so that fluid from a flow cell can enter the waste basin and then exit under gravity to a waste drain (50).
