Procedure 6 Determination of cadmium concentration and pH value in aqueous solutions by means of a handheld light-addressable potentiometric sensor (LAPS) device

Abstract

Publisher Summary This chapter discusses the fabrication of a light-addressable potentiometric sensor (LAPS) for the detection of the pH value and the cadmium-ion concentration in aqueous solutions. For the pH-sensitive LAPS, use, e.g., Ta 2 O 5 as a sensor membrane, and for the cadmiumselective LAPS, use a Cd 2+ -selective chalcogenide glass thin film as a heavy metal-sensitive material. The electrochemical sensor characterization of the LAPS structure performs current vs. voltage (I/V) and constant current (CC) measurements. The presented protocol provides a basic idea of a typical LAPS set-up. The number of measurement spots and the size of the sensor chip can vary for different applications. The position of the light sources as well as the position of the amplifier stage is of great importance for the signal stability and should be as close as possible to the sensor chip. Furthermore, the conductivity of the electrolyte solution has to be taken into account for low conductive solutions. The initial I/V and CC measurements, as demonstrated in this protocol, are important to evaluate the system performance and provide a wide range of useful information.