Potentiometric biosensor for lysine analysis based on a chemically immobilized lysine oxidase membrane

An enzymatic lysine electrode is developed for the potentiometric analysis of lysine (Lys). This lysine biosensor consists of a chemically immobilized lysine oxidase membrane attached to an all-solid-state ammonium electrode. In this system, the enzymatic degradation of lysine produces ammonia, which is then detected with the ammonium electrode. The influence of immobilization conditions on the potentiometric response and the lifetime of the electrode was studied. Under optimal conditions, the relationship between the potentiometric response and the log [Lys] was linear between 3x10(-5) and 10(-3) M, the sensitivity was 50 mV/decade, the repeatability 1.4%, and the response time t(95%) was 15 s. (C) 1998 Elsevier Science B.V, All rights reserved.