ISFET microsensors for the detection of pollutants in liquid media

Different types of polymeric matrices were tested in order to optimize the characteristics of the specific ISFETs developed for the detection of an io nic pollutant, the ammonium ion and of a molecular pollutant, the trichlorf on which is a common organophosphorus pesticide. A miniaturized sensor for ammonium detection, based on the integration of both ammonium and reference FETs in a single chip, was fabricated. A differential measurement mode bet ween both FETs was used, this mode of measurement allowed to reduce interfe rences of Na+ and K+ ions, the effect of ionic strength and of temperature. The sensitivity of the ammonium detection was around 30 mV/pNH(4)(+) and t he detection limit 2 x 10(-6) M. Trichlorfon as a common pesticide is detec ted using a BuChE-FET sensor which is prepared either with cross-linked BSA -glutaraldehyde membrane or photocross-linkable PVA/SbQ (poly(vinyl alcohol ) containing styrylpyridinium) membrane. PVA/SbQ membrane shows better char acteristics compared to BSA membrane: larger linear dynamic range in kineti c mode, better reproducibility, and above all, better stability in storage. Nevertheless, both membranes present the same detection limit for trichlor fon: 10(-6) M. (C) 1999 Elsevier Science S.A. All rights reserved.