Estimation of lactate in meat extracts by screen-printed sensors

Various facets of sensor technology: platinum dispersed on carbon, a second "blank" working electrode, polymer matrices for enzymes and diffusion-limi ting membranes, were integrated using screen-printing to produce lactate se nsors. The enzyme was lactate oxidase. The polymer matrices were hydroxyeth yl cellulose, GafQuat/lactitol and hydroxyethyl cellulose/polyethyleneimine . The outer membrane was of known composition: polyvinyl chloride co-polyme r/cellulose acetate butyrate. When the sensors were mounted in a flow injec tion analyser, estimates were obtained of the lactate concentration in simp le buffer extracts of cattle meat. The most accurate estimates were obtaine d from sensors in which the enzyme was embedded in a matrix of GafQuat/lact itol or hydroxyethyl cellulose/polyethyleneimine. The currents generated by the enzyme in the matrices containing GafQuat or polyethyleneimine were hi gher than when hydroxyethyl cellulose alone was used as a matrix. The activ ity of the sensors under dry storage (over silica gel at 25 degrees C) vari ed over eight months, but remained at a functional level. Every step in the se relatively simple sensors was achieved by screen-printing; the use of a "blank" working electrode avoided the necessity of additional layers or mem branes to reject interferents and the flow injection analyser provided a co nstant hydrodynamic environment for sensor function. (C) 1999 Elsevier Scie nce B.V. All rights reserved.