Rochdi Kherrat

Highly sensitive electrochemical biosensor for bisphenol A detection based on a diazonium-functionalized boron-doped diamond electrode modified with a multi-walled carbon nanotube-tyrosinase hybrid film

A highly sensitive electrochemical biosensor for the detection of Bisphenol A (BPA) in water has been developed by immobilizing tyrosinase onto a diazonium-functionalized boron doped diamond electrode (BDD) modified with multi-walled carbon nanotubes (MWCNTs). The fabricated biosensor exhibits excellent electroactivity towards o-quinone, a product of this enzymatic reaction of BPA oxidation catalyzed by tyrosinase. The developed BPA biosensor displays a large linear range from 0.01 nM to 100 nM, with a detection limit (LOD) of 10 pM. The feasibility of the proposed biosensor has been demonstrated on BPA spiked water river samples. Therefore, it could be a promising and reliable analytical tool for on-site monitoring of BPA in waste water.

Development of an ammonium ISFET sensor with a polymeric membrane including zeolite

Abstract This paper presents a first report on an ammonium ISFET (ion-sensitive field effect transistor) based on a polymeric membrane (siloprene) including a zeolite selective for ammonium exchange: clinoptilolite. The effect of zeolite content on sensitivity of detection is studied; an optimum is obtained for 43 w/w%. A sensitivity of detection of 32 mV/pNH 4 + and a detection limit of 10 −8 M are obtained. A highly selective ammonium ISFET is obtained.

Elaboration and standardization of an optical fibre corrosion sensor based on an electroless deposit of copper

Abstract The goal of our present work is to develop and test an optical fibre corrosion sensor (OFCS) fabricated by an electroless copper film deposition onto an optical fibre core within the sensing region. In our case, corrosion monitoring was carried out by two methods: optical and electrochemical methods. The idea consists is to couple these two methods by correlating the parameters describing the optical detection and those which describe the electrochemical corrosion process. This approach, once is carried out, makes it possible to gain more precise information on degradation within hidden parts of metallic structures.

Sensitive impedimetric biosensor for direct detection of diazinon based on lipases

Two novel impedimetric biosensors for highly sensitive and rapid quantitative detection of diazinon in aqueous medium were developed using two types of lipase, from Candida Rugosa (microbial source) (CRL) and from porcine pancreas (animal source) (PPL) immobilized on functionalized gold electrode. Lipase is characterized to specifically catalyze the hydrolysis of ester functions leading to the transformation of diazinon into diethyl phosphorothioic acid (DETP) and 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMHP). The developed biosensors both presented a wide range of linearity up to 50 μM with a detection limit of 10 nM for Candida Rugosa biosensor and 0.1 μM for porcine pancreas biosensor. A comparative study was carried out between the two biosensors and results showed higher efficiency of Candida Rugosa sensor. Moreover, it presented good accuracy and reproducibility, had very good storage and multiple use stability for 25 days when stored at 4°C.

A microconductometric biosensor based on lipase extracted from Candida rugosa for direct and rapid detection of organophosphate pesticides

Organophosphate pesticides (OPs) have been intensively used as insecticides in agriculture; after entering the aquatic environment, they may affect a wide range of organisms. A conductometric enzymatic biosensor based on lipase extracted from Candida rugosa (CRL) has therefore been developed for the direct and rapid quantitative detection of organophosphate pesticides: diazinon, methyl parathion and methyl paraoxon in water. The biosensor signal and response time were obtained under optimum conditions, the enzyme being immobilised in the presence of gold nanoparticles. Under these conditions, the enzymatic biosensor was able to measure concentrations as low as 60 µg/L of diazinon, 26 µg/L of methyl parathion and 25 µg/L of methyl paraoxon very rapidly (response time: 3 min). Moreover, this CRL biosensor was not sensitive to interferences such as carbamates. It presented good storage stability for 21 days when kept at 4°C and it was successfully applied to real samples.

Functionalization of ISE Sensor for Metal Ion Detection

In this work, we report the study of functionalized platinum (Pt) electrodes based on a polymeric membrane (PVC) including an ionophore (ethyln diamin tetracetic EDTA) sensitive for mercury ions Hg2+. The optimised working conditions of the sensors have been studied with regard to the sensitivity performances; in particular, the polarisation was adjusted to - 0.2V/SCE. Ion sensitivity of sensors have been tested for Hg(II) via Cd(II) in aqueous solution. A layer of EDTA deposited on platinum electrode has been characterised by impedance spectroscopy and cyclic voltammetry methods.

ELECTROCATALYTIC OXIDATION OF ASCORBIC ACID AT POLYPYRROLE THIN FILM INCORPORATING PALLADIUM PARTICLES

In this paper, we report a simple sensing strategy for electrochemical determination of ascorbic acid (AA) using a combination of polypyrrole (PPy) thin film and palladium particles composites deposited onto n-doped silicon (Si) substrate. A two-step electrochemical process was employed to synthesize the composite films: At first, PPy film (average thickness 200nm) was electrogenerated on Si substrate from an organic solution of the pyrrole under galvanostatic conditions. Secondly, palladium particles were electrodeposited on PPy/Si surface from a separate solution by chronoamperometry technique. The surface morphology analysis of the obtained composites shows a uniform dispersion of palladium particles onto the polymer matrix and reveals that the electrodeposition time has a significant effect on the amount and size of the incorporated palladium particles. The electrochemical reactivity of the Pd–PPy/Si-modified electrodes towards the oxidation of AA was studied by cyclic voltammetry method in 0.1M, pH 7.0 phosphate buffer solution. The oxidation current was proportional to the concentration of AA in the range of 0.5–10mM with a detection limit of 0.2mM.

Impedimetric Biosensor for the Determination of Phospholipase A2 Activity in Snake Venom

ABSTRACT An impedimetric biosensor to determine the activity of phospholipase A2 has been developed for the first time. This biosensor is based on the immobilization of enzyme phospholipase A2 (PLA2) from snake venom on the surface of a gold electrode. The enzymatic reaction takes place in the presence of L-α-phosphatidylcholine (lecithin) substrate, in 10 mM pH 7.4 phosphate buffer. The impedance of enzymatically modified electrode/electrolyte interface increased as the concentration of lecithin increases. A detection limit of 10−11 M and a linear range of 10−10 to 10−5 M were obtained. At a fixed concentration of lecithin (10−3 mM), when the PLA2 enzyme with a certain level of activity is injected, the impedance of the enzymatically modified electrode/electrolyte interface changed in the inverse direction, due to the competitive effect of injected PLA2 enzyme. A linear range of 10 to 400 ng/L (corresponding to 16 to 640 U/L) was obtained for commercial naja mossambica mossambica snake venom. The activity of PLA2 from naja cobra snake venom (Origin Thailand) was determined to be 75% of that of naja mossambica mossambica snake venom.