DURABLE NH4+-SENSITIVE CHEMFET

This paper describes the development of a durable NH4+-sensitive CHEMF ET based on various membrane materials incorporating nonactin as the i onophore and (tetrakis-(4-chloryhenyl)borate anions as ionic sites. Th e ISFETs used in this study have the SiO2 gate covered with an interme diate hydrogel layer of polyHEMA. The CHEMFETs based on the Siloprene showed NH4+ responses with the almost Nernstian slope in the range of activity 10(-4)-10(-1) in the presence of 0.1 M Na+ (log K(NH4, Na)(po t) = -2.8) and good selectivity even after 22 months of continuous exp osure io conditioning electrolyte. (C) 1997 Elsevier Science S.A.