A dual-phase biosensing system for the determination of phenols in both aqueous and organic media

A dual-phase amperometric, biosensing device, incorporating immobilised tyrosinase, has been developed for the detection of phenolic compounds in both the aqueous and organic phases. The all-in-one biosensing probe, in which the electrodes, enzyme and buffer all reside behind a hydrophilic dialysis membrane, allowed direct analysis in the organic phase without the need for deliberately added electrolyte. The design also allowed analyses in both batch and flow injection measurement modes. In aqueous solutions, the unique configuration of the sensing device enabled the direct determination of I nM (0.1 mug l(-1)) phenol in batch mode and 10 nM (1 mug l(-1)) phenol in flow injection mode. Linearity of response over five orders of magnitude was also achieved. Relative responses for a range of phenolic compounds are also reported. In organic solvents, the sensitivity, linear range and response time were all shown to be very much dependent on the relative hydrophobicity of the solvents and substrates investigated. The effect of hydration for the immobilisation layer in the organic phase was also addressed. (C) 2001 Elsevier Science B.V. All rights reserved.