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Phenolic compounds such as catechol are present in a wide variety of foods and beverages; they are of great importance due to their antioxidant properties. Their consumption protects against the development of certain diseases such as cancer and cardiovascular diseases. A MIP chitosan (CS) film has been electrodeposited on a boron doped diamond (BDD) electrode, by chronoamperommetry in the presence of catechol, followed by elution with 0.1 M KCl. The morphology of the MIP and non-MIP (NIP) film has been studied by AFM. The electrochemical response of the sensor analyzed by cyclic voltammetry (CV) indicates that the sensor shows excellent reproducibility (RSD = 4.1%) and repeatability (RSD = 7.0%) for catechol detection in the range of 0 to 80 μM, with a detection limit of 6.9 × 10−7 M and high selectivity to catechol recognition versus different phenolic compounds. The results obtained in a red wine show that it can detect catechol in a complex matrix.

International audience; Ammonium exchange with hybrid PVC-bentonite (mineral montmorillonite clay) thin film was revealed using FTIR spectroscopy, EDX, cyclic voltammetry and electrochemical impedance spectroscopy. The effect of ammonium exchange on the charge transfer resistance of PVC-bentonite hybrid thin film was attributed to a modification of the intersheet distance and hydration of bentonite crystals. The obtained impedimetric ammonium sensor shows a linear range of detection from 10(-4)M to 1M and a detection limit around 10(-6)M.

We report the use of ion-selective field effect transistor devices (ISFETs) with an integrated pseudo-reference electrode for on-line monitoring of bacterial metabolism by monitoring of the pH variation. As a model we tested the ability of Lactobacillus strains to ferment sugars, producing lactic acid, which results in a decrease in pH in the suspension medium. We have tested and compared sugar uptake by L. sakei and a L. curvatus strains. The results obtained show that it is possible to distinguish between both types of Lactobacillus strains through their pattern of ribose uptake. The use of ISFETs represents a non-invasive methodology that can be used to monitor biological activity in a wide variety of systems.

A hexavalent chromium-sensitive EMIS sensor (electrolyte membrane insulator semiconductor sensor) is prepared by deposition of a tributylphosphate (TBP) ionophore-containing siloprene membrane on a Si/SiO2/Si3N4 structure. The developed EMIS sensor was studied by means of impedance spectroscopy, capacitance–voltage, X-ray photoelectron spectrometry and FT-IR spectroscopy. From the flat-band shift of the EMIS structure, the nersntian response to the anionic species Cr2O7− was demonstrated. The linear range of detection is 10− 4 M to 10− 1 M and the detection limit is 10− 5 M. Sulfate and chloride anions are shown not to be interfering whereas carbonate ions present a pKpot equal to 0.19.

Protein selective potentiometric microelectrodes with the PPy[3,3-Co(1,2-C2B9H11)(2) solid internal contact were fabricated by the immobilization of different proteinases such as trypsin, pronase E and carboxypeptidase B on the surface of platinum microelectrodes modified by a conducting polymer. The performance of these biosensors was investigated by using potentionnetric measurements. The feasibility of this biosensor for protein determination was demonstrated, with a detection limit of about 1-2 mu g/ml for prolamine in buffer solution.

International audience; A novel impedimetric immunosensor for the detection of haemoglobin has been developed by mixed self-assembled monolayers on An. First, a mixed self-assembled monolayer (SAMs) consisting of 1,2 dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(biotinyl) (biotinyl-PE) and 16-mercaptobexadecanoic acid (MHDA) on gold electrodes was studied. The conformational properties of the SAMs were characterised by cyclic voltammetry and impedance spectroscopy. After blocking non-specific binding sites in the mixed monolayer using non-specific IgG, neutravidin was used to bind to biotinyl sites present in the mixed monolayer. Finally, biotinylated anti-haemoglobin IgG was immobilised to the tethered neutravidin. The membrane resistance R-m, obtained from the assembly, decreased gradually after the addition of non-specific IgG, neutravidin and anti-haemoglobin to the monolayer. This decrease could be attributed to a rearrangement in the structure of the SAMs. The detection of antibody-antigen reaction demonstrates that the potentiometric immunosensor exhibited high sensitivity and a detection limit of 20 ng/ml (approximately 0.3 nM). (c) 2005 Elsevier B.V. All rights reserved.

The development and preliminary evaluation of an integrated microanalytical system based on electrochemical detection and cell positioning is reported here. The chip includes ion-sensitive field effect transistors (ISFET), a single pair of castellated microelectrodes and a reference Ag/AgCl microelectrode. The ISFETs have shown good operating characteristics, with a 52 mV/pH response. Yeast cells and bacteria have been positioned on the gate region of the ISFET sensor using single pair of castellated microelectrodes.

The new macrocycles 4-phenyl-11-(1-oxodecyl)-1,7-dithia-11-aza-4-phosphacyclotetradecane (III) and 4-phenyl-4-sulfide-11-(1-oxodecyl)-1,7-dithia-11-aza-4-phosphacyclotetradecane (IV) have been synthesised and characterised. Through their use as ionophore in an all-solid state poly(vinylchloride) matrix membrane electrode, the ability of IV as cation receptor has been studied. The electrode exhibits a Nernstian response towards copper (II) ions with a cationic slope of 30.7 ± 1.7 mV per decade, over the concentration range 3.0 × 10 − 6 to 1.0 × 10 − 2 M and the potential response remains almost unchanged over the pH range 3.9–6.4. The electrode can be used for at least seven months without a considerable alteration in its potential.

Planar all-solid-state hydrogen sensing microelectrodes have been constructed and investigated. A novel conductive polymer, polypyrrole (PPy) doped with cobaltabis(dicarbollide) ions ([3,3′-Co(1,2-C 2 B 9 H 11 ) 2 ] − ), thin film was galvanostatically grown over a solid substrate (Pt) and acted as an internal solid contact layer between the solid surface (Pt) and the polymeric sensitive membrane. The potentiometric response characteristics of this new kind of microelectrode based on tri- n -dodecylamine (TDDA) ionophore were evaluated. They exhibited excellent selectivity for the primary ion and a linear response over the pH range 3.5–11.0 with a slope of 52 ± 2 mV decade − 1 . The selectivity properties have been examined. The results obtained were comparable to that of a conventional ion-selective electrode (ISE) based on the same ionophore.

Potassium (K + ) ion-sensitive membranes produced by the ion implantation technique are investigated. The sensing layers are fabricated by implanting K + and Al + ions into silicon dioxide on silicon with low energy in order to reduce the damage to the substrate during the process of implantation. The ion sensitivity of such ion-implanted layers was investigated by using C – V measurements. All devices tested have shown good sensitivities and linear responses over at least four decades of potassium activity, with good selectivity in the presence of interfering ions like NH 4 + , Li + and Mg 2+ .

International audience; This paper presents a first report on chromium ISFET (ion-sensitive field effect transistor) based on a polymeric membrane (siloprene) including an ionophore (tributylphosphate) sensitive for hexavalent chromium. The sensor sensitivity as a function of the pH was studied; its value is minimum in a pH interval from 5.5 to 7.5. The sensitivity for hexavalent chromium was found to be 15 mV/Ioga(Cr6+) in the range of 10(-4) to 10(-2) M. The detection limit was found to be 10(-5) M. The studied interfering ions are Pb(II) and Cd(II) that do not represent a great perturbation upon the response for hexavalent chromium. (c) 2005 Elsevier B.V. All rights reserved.