Instrument with integrated sensors for a rapod determination of inorganic ions

Abstract

Abstract A rapid determination of different analytically relevant parameters is of increasing interest in medical and environmental applications. A simple and easy-to-handle instrument replaces more and more complex laboratory analytical systems. The advantages of such portable instruments 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 compact battery instrument with interchangeable chemical sensors for the direct potentiometric determination of different analytically relevant 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. The data are transferred by an SPI serial interface. The software programming was done in our institute. Before measuring the sample a two-point calibration has to be carried out, the data being stored in the microprocessor. The transducers for the ion-selective planar sensor strips are manufactured using thick-film technology with integrated receptor and refences electrodees 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 recessed miniaturized electrode.