Simultaneous monitoring of glucose and lactate by an interference and cross-talk free dual electrode amperometric biosensor based on electropolymerized thin films

An interference and cross-talk free dual electrode amperometric biosensor i ntegrated with a microdialysis sampling system is described, for simultaneo us monitoring of glucose and lactate by flow injection analysis. The biosen sor is based on a conventional thin layer how-through cell equipped with a Pt dual electrode (parallel configuration). Each Pt disk was modified by a composite bilayer consisting of an electrosynthesised overoxidized polypyrr ole (PPYox) anti-interference membrane covered by an enzyme entrapping gel, obtained by glutaraldehyde co-crosslinking of glucose oxidase or lactate o xidase with bovine serum albumin. The advantages of covalent immobilization techniques were coupled with the excellent interference-rejection capabili ties of PPYox. Ascorbate, cysteine, urate and paracetamol produced lactate or glucose bias in the low micromolar range; their responses were, however, completely suppressed when the sample was injected through the microdialys is unit. Under these operational conditions the flow injection responses fo r glucose and lactate were linear up to 100 and 20 mM with typical sensitiv ities of 9.9 (+/- 0.1) and 7.2 (+/- 0.1) nA/mhil, respectively. The shelf-l ifetime of the biosensor was at least 2 months. The potential of the descri bed biosensor was demonstrated by the simultaneous determination of lactate and glucose in untreated tomato juice samples; results were in good agreem ent with those of a reference method. (C) 2000 Elsevier Science S.A. All ri ghts reserved.