Piezoelectrically driven micromachined silicon pumps are shown to have excellent characteristics for application in miniaturized chemical analysis systems. A system is demonstrated using two micro pumps and a separate glass flow-through cell with a potassium-sensitive ISFET. The measurement protocol is such that the sample solution enters the detector but does not pass the sensitive pump valves, thus improving the practical applicability of the system. During its operation, the sensor is continuously calibrated with a very low consumption of calibrating solution. With a measurement rate of four samples per minute, the use of calibrant is less than 3 ml/h.