INSTRUMENT WITH INTEGRATED SENSORS FOR A RAPID-DETERMINATION OF INORGANIC-IONS

A rapid determination of different analytically relevant parameters is of increasing interest in medical and environmental applications. A s imple and easy-to-handle instrument replaces more and more complex lab oratory analytical systems. The advantages of such portable instrument s with integrated disposable sensors are the flexibility for measuring on the spot, fast response time given by the miniaturized sensors and low costs for procuring and running. The paper presents a portable co mpact battery instrument with interchangeable chemical sensors for the direct potentiometric determination of different analytically relevan t inorganic ions, such as nitrate and potassium. The battery measuring instrument consists of an 8-bit microprocessor with a 12-kbyte EPROM on chip and a 12-bit sampling A/D converter with internal reference. T he data are transferred by an SPI serial interface. The software progr amming was done in our institute. Before measuring the sample a two-po int calibration has to be carried out, the data being stored in the mi croprocessor. The transducers for the ion-selective planar sensor stri ps are manufactured using thick-film technology with integrated recept or and reference electrodes on the chip. The reference electrode shows a high long-term stability as disturbing ions have to diffuse through a reference channel filled with a hydrogel in order to reach the rece ssed miniaturized electrode.