Chemically modified field effect transistors to monitor ion concentration in nutrient solutions

Abstract

Closed soilless growing systems are introduced on a large scale in horticultural production, to decrease environmental pollution and to increase efficiency and product quality. Applying closed growing systems needs precise knowledge of the composition of the recirculating nutrient solution. This paper presents basic principles of a measur-ing system, which can monitor continuously the concentration of nutrients in water. The sensor system is based on the chemically modified field effect transistor (CHEMFET) that replaces current methods of discontinuous sampling followed by analysis in the laboratory. For obtaining sensors of high durability, polysiloxane membranes have been developed which contain different side groups to tune their intrinsic properties. These polysiloxane membranes show good performance in lifetime experiments. The ion selectivity has been tuned by incorporation of various novel ion receptor molecules, yielding sensors with high selectivity’s for sodium, potassium, calcium, nitrate, phos-phate and dihydrogen phosphate