A peroxidase-tetrathiafulvalene biosensor based on self-assembled monolayer modified Au electrodes for the flow-injection determination of hydrogen peroxide

The construction and performance under flow-injection conditions of an integrated amperometric biosensor for hydrogen peroxide is reported. The design of the bioelectrode is based on a mercaptopropionic acid (MPA) self-assembled monolayer (SAM) modified gold disk electrode on which horseradish peroxidase (HRP, 24.3 U) was immobilized by cross-linking with glutaraldehyde together with the mediator tetrathiafulvalene (TTF, 1 mu mol), which was entrapped in the three-dimensional aggregate formed. The amperometric biosensor allows the obtention of reproducible flow injection amperometric, responses at an applied potential of 0.00 V in 0.05 mol L-1 phosphate buffer, pH 7.0 (flow rate: 1.40 mL min(-1), injection volume: 150 mu L), with a range of linearity for hydrogen peroxide within the 2.0 x 10(-7) -1.0 x 10(-4) mol L-1 concentration range (slope: (2.33 +/- 10.02) x 10(-2) A mol(-1) L, r = 0.999). A detection limit of 6.9 x 10(-8) mol L-1 was obtained together with a R.S.D. (n = 50) of 2.7% for a hydrogen peroxide concentration level of 5.0 x 10(-5) mol L-1. The immobilization method showed a good reproducibility with a R.S.D. of 5.3% for five different electrodes. Moreover, the useful lifetime of one single biosensor was estimated in 13 days. The SAM-based biosensor was applied for the determination of hydrogen peroxide in rainwater and in a hair dye. The results obtained were validated by comparison with those obtained with a spectrophotometric reference method. In addition, the recovery of hydrogen peroxide in sterilised milk was tested. (c) 2005 Elsevier B.V. All rights reserved.