To produce a small-volume flow-type measuring cell with favourable flow in a sensor array for determining a substrate concentration in a sample medium with a membrane-covered enzyme electrode and a reference electrode which are in contact with the measuring cell, it is proposed that the reference electrode is outside the membrane covering of the enzyme electrode and that the maximum extension of the flow-type measuring cell in the direction normal to the flow direction of the sample medium is essentially equal to the diameter of the sensitive layer of the enzyme electrode. …<IMAGE>…
