Journal of Biotechnology, 27 (1993) 117-127 117 © 1993 Elsevier Science Publishers B.V. All rights reserved 0168-1656/93/$06.00 BIOTEC 00803 Development of a flow injection analysis mediated biosensor for sulfite C.A. Groom, J.H.T. Luong and C. Masson Biotechnology Research Institute, National Research Council Canada, Montreal, Quebec, Canada (Received 20 December 1991; accepted 23 March 1992) Summary Among several mediators tested including N,N,N',N'-tetramethyl-l,4-phenyl- enediamine, 2,3,5,6-tetramethyl-l,4-phenylenediamine, tris(2,2'-bipyridyl)ruthe- nium(II) chloride hexahydrate and 2,6-dichlorophenolindophenol, an organic con- ducting salt of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) was selected to form a mediated biosensor for sulfite in view of its superior mediating capability to sulfite oxidase. The conducting TCNQ/TTF organic salt and sulfite oxidase were sequentially deposited onto the sensing area of a vitreous carbon electrode which was then covered by a dialysis membrane (MW cut-off 6000-8000). The mediated TCNQ/TTF working electrode was used in connection with flow injection analysis for the determination of sulfite. The linear range of the system was 0 to 5 mM with a detection limit of 5 ~M. The electrode achieved 90% of maximum response in 20 s, but required 10 rain to return to baseline. The system was tested for 55 repeated analyses during 26 h of continuous operation with no loss of activity. Electrodes bearing both the conducting salt and sulfite oxidase stored in 3 M ammonium sulfate and at 4°C retained 100% of their original activity after 2 months. The biosensor system was applicable for the determination of sulfite in wine, beer and dried fruit samples and the data obtained agreed very well with the pararosaniline reference method. Sulfite; Sulfite oxidase; Tetrathiafulvalene (TTF); Tetracyanoquinodimethane (TCNQ); Mediated biosensor; Mediator; Amperometric electrode Correspondence to: J.H.T. Luong, Biotechnology Research Institute, National Research Council Canada, Montreal, Que. M4P 2R2, Canada.