Available online at www.sciencedirect.com Sensors and Actuators B 131 (2008) 394–402 Inhibitive determination of metal ions by an amperometric glucose oxidase biosensor Study of the effect of hydrogen peroxide decomposition Maria Rachele Guascito ∗ , Cosimino Malitesta, Elisabetta Mazzotta, Antonio Turco Dipartimento di Scienza dei Materiali, Universit` a del Salento, Via Arnesano, 73100 Lecce, Italy Received 1 August 2007; received in revised form 15 November 2007; accepted 25 November 2007 Available online 3 December 2007 Abstract An amperometric glucose biosensor based on glucose oxidase immobilized in electrosynthesized poly-o-phenylenediamine was successfully applied to the determination of a wide group of heavy metals of environmental interest. The inhibition effects of Hg 2+ , Ag + , Cu 2+ , Cd 2+ , Pb 2+ , Cr 3+ , Fe 3+ , Co 2+ , Ni 2+ , Zn 2+ , Mn 2+ and also CrO 4 2- on glucose oxidase were studied. Collected data showed a reversible inhibition mechanism. Results about the quantitative analysis of metal ions in terms of detection limit, linear range, sensitivity and R.S.D. are discussed for each tested metal ion. The biosensor was able to discriminate two different oxidation states of chromium being able to reject Cr 3+ and to detect the toxic species CrO 4 2- . Also biosensor storage stability and response reproducibility were investigated. Moreover, this study represents the first attempt of evaluating the effect of the hydrogen peroxide decomposition by metal ions on the response of an enzymatic biosensor based on the amperometric detection of the hydrogen peroxide. Experiments were performed with the aim to quantitatively evaluate, for any single metal ion, if this process is competitive with the inhibition of enzymatic reaction in the adopted experimental conditions. © 2007 Elsevier B.V. All rights reserved. Keywords: Heavy metal ions; Glucose oxidase; Inhibition; Amperometric biosensor; Hydrogen peroxide 1. Introduction The pollution caused by heavy metals is considered a priority in environmental monitoring. Several heavy metals can accumu- late in the biosphere and transfer to the alimentary chain, arising potential serious health consequences for human beings, ani- mals and plants. Their determination at trace level can be carried out with several analytical techniques like atomic absorption spectroscopy, inductively coupled plasma optical emission or with chromatographic techniques coupled to mass spectrome- try. The choice of the technique is determined by several factors that can constitute an important impediment for their effective application. In such context, electrochemical sensors and biosensors appear the appropriate alternative, or at least a complementary choice, with respect to the mentioned traditional techniques. ∗ Corresponding author. E-mail address: maria.rachele.guascito@unile.it (M.R. Guascito). They have the advantage of specificity, low cost, easy use; moreover they can be used in real time in the field. Among biosensors developed for environmental application, enzyme inhibition-based sensors have been widely studied. In particu- lar, for determination of mercury and its compounds, several enzymes were used for inhibitive determination, e.g. ure- ase [1,2], peroxidase [3,4], xanthine oxidase [5], invertase [6–9], butyrycholinesterase [10], isocitric dehydrogenase [11], glucose oxidase [10,12–14] and invertase with glucose oxi- dase [15 and references therein]. A complete review on this topic has been recently published [16]. Recently our research group has presented results related to the original applica- tion of an established amperometric glucose biosensor based on glucose oxidase immobilized in electrosynthesized poly- o-phenylenediamine (Pt/PPD/GOx) for the determination of Hg 2+ by an inhibition detection scheme [14]. A low response time and a rapid recovery of response by EDTA seem the most interesting characteristics of the proposed biosensor, along with the well known easy preparation of this kind of biosensors. 0925-4005/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2007.11.049