ABSTRACT
Several kinds of modified carbon screen printed electrodes (CSPEs) for amperometric detection of hydrogen peroxide (H2O2) are presented in order to propose a methyl mercaptan (MM) biosensor. Unmodified, carbon nanotubes (CNTs), cobalt phthalocyanine (CoPC), Prussian blue (PB), and Os-wired HRP modified CSPE sensors were fabricated and tested to detect H2O2, applying a potential of +0.6 V, +0.6 V, +0.4 V, -0.2 V and -0.1 V (versus Ag/AgCl), respectively. The limits of detection of these electrodes for H2O2 were 3.1 µM, 1.3 µM, 71 nM, 1.3 µM, 13.7 nM, respectively. The results demonstrated that the Os-wired HRP modified CSPEs gives the lowest limit of detection (LOD) for H2O2 at a working potential as low as -0.1 V. Os-wired HRP is the optimum choice for establishment of a MM biosensor and gives a detection limit of 0.5 µM.
Subject(s)
Biosensing Techniques/instrumentation , Hydrogen Peroxide/analysis , Sulfhydryl Compounds/analysis , Catalysis , Electrochemical Techniques , Electrodes , Ferrocyanides/chemistry , Horseradish Peroxidase/metabolism , Indoles/chemistry , Nanotubes, Carbon/chemistry , Organometallic Compounds/chemistry , Osmium/chemistry , Oxidation-ReductionABSTRACT
Lagoons and coastal waters are contaminated by a large number of chemicals discharged directly or carried by rivers and runoff water that drain catchment areas in which agricultural activities take place. The inflow of these exogenous compounds constitutes a genuine risk for the health of ecosystems. It is therefore important to detect their presence in the natural environment before they cause irreversible damage. Here we present a study aimed at developing a tool for rapid detection of pesticides and other chemicals in environments liable to be contaminated, in order to propose an early warning system for decision-makers. The study carried out focuses on two herbicides commonly encountered in the environment, i.e. diuron and glyphosate, as well as several of their photodegradation products (DCPU, DCPMU, AMPA). The results presented contribute toward developing a biosensor based on measuring the metabolic activities of immobilized unicellular marine algae. The sensor's operation is based on measuring the esterase localized on the external membrane of the algae cells and chlorophyll fluorescence. The tests carried out show that the signal emitted by the sensor is disturbed by the presence of the two herbicides studied. The system proposed appears useful as a tool for controlling environments requiring monitoring.