Ali Zazoua

Cadmium-sensitive electrode based on tetracetone derivatives of p-tert-butylcalix[8]arene.

The performance of a cadmium-sensitive electrode based on the tetracetone derivatives of p-tert butylcalix[8]arene was investigated. The ion-sensitivity of the calix[8]arene was examined via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectrometry, UV/Vis spectroscopy and FT-IR spectroscopy. The sensitive membrane containing the active ionophore was cast onto the surface of a gold electrode. The electrode exhibited a linear relationship between the charge transfer resistance (Rct) and the logarithm of the detected ion concentration. The cathodic peak at a potential of 0.56 V increased linearly as the Cd(2+) ion concentration increased. The detection limit of the device reached 10(-7) M with high sensitivity toward cadmium.

A High Sensitivity Impedimetric Biosensor Using the Tannin From Quercusmacrolepis as Biorecognition Element for Heavy Metals Detection

A new poly(vinylchloride) (PVC) membrane electrode based on tannin from the bark of Quercusmacrolepis (acorn) as the ionophore was prepared and modified onto the surface of a gold electrode. The electrochemical impedance spectroscopy (EIS) technique was used to study the sensitivity of the electrode that was modified with a thin layer of polymeric biomembrane, in order to detect heavy metals ions in solution. The device shows a good sensitivity for Zn²⁺, Ni²⁺ ions and a little less for Cd²⁺. The electrode indicates a good linear response for the three metals over a wide concentration range from 1.0×10^-9 to 1.0×10^-4 M, with a detection limit of 1.0×10^-9 M.

Evidence of ammonium ion-exchange properties of natural bentonite and application to ammonium detection

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.

An enzyme biosensor based on beta-galactosidase inhibition for electrochemical detection of cadmium (II) and chromium (VI)

ABSTRACT The focus of this article is the development and optimisation of a simple, sensitive, selective biosensor for the detection of heavy metals, through inhibition of β-galactosidase (β-gal) from Aspergillus oryzae after its immobilisation on an electrochemical transducer by cross-linking with glutaraldehyde. The inhibition of β-gal by Cd(II) and Cr(VI) was demonstrated by the decrease of β-gal activity monitored by the conductometric signal. Under optimal conditions, the developed voltammetric and impedimetric biosensor, based on the specific interaction of metallic ions with beta-galactosidase that increases the electron transfer of the redox probe, presented a wide range of linearity. Detection limits of 3.12 × 10–10 M (91.7 ng/L) were obtained, using both techniques, for Cr(VI). For Cd(II) detection limits were 2.85 × 10–8 M (6.95 µg/L) using EIS and 3.22 × 10–11 M (7.61 ng/L) using square wave voltammetry (SWV).

Electrochemical Determination of Cadmium, Lead, and Nickel Using a Polyphenol-Polyvinyl Chloride – Boron-Doped Diamond Electrode

ABSTRACT Boron-doped diamond electrode surfaces were modified by a polyphenol—polyvinyl chloride membrane. The polyphenols were extracted from the skin of acorns, the fruit of the oak tree. The polymer film was applied on the boron-doped diamond electrode surface by solvent evaporation. The resulting polyphenol–polyvinyl chloride–boron-doped diamond electrode was used as a sensor for cadmium, lead, and nickel. The synergy between the chemically modified surfaces and electrochemical performances of the boron-doped diamond microcell electrode was examined by differential pulse anodic stripping voltammetry at nanomolar concentrations of the three metal ions. The modified electrode provided a stable, sensitive, and selective response to cadmium, lead(II), and nickel(II) ions. The resulting detection limits were 0.0221, 0.25, and 0.00424 nmole L−1, respectively.

A new sensitive and selective sensor for heavy metal ions based on tannin extracted from the skin of Punica granatum L

ABSTRACT This article presents the development of a sensor made from a gold electrode and a receiving polymeric membrane based on tannin extracted from the skin of Punica granatum. L (pomegranate) for real-time detection of heavy metals in a hydrous environment. The basic principle of this device is the complexing (chelating) of metal ions through the adjacent hydroxyl groups contained in the chemical structures of the tannins. The electrochemical characterisation was performed by using electrochemical impedance spectroscopy and square wave voltammetry. Other morphological and structural analyses were performed by using Fourier transform infrared spectroscopy and atomic-force microscopy. The results obtained showed the high sensitivity of the developed device (detection limits of 6.35 × 10−9 g L−1 for Cu2+, 1.1 × 10−8 g L−1 for Cd2+ and 2 × 10−7 g L−1 for Pb2+) and the possibility of simultaneously detecting several heavy metals, each one in a highly selective manner with highly acceptable response time (48s).

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.

Polyphenolic Natural Products for the Electrochemical Determination of Cadmium

ABSTRACT The goal of this study is to characterize the polyphenolics of the extracts from the skin of Punica granatum L. (pomegranate) and Quercus suber (cork oak). The measurements were performed quantitatively and complexing reactions with metals were characterized for use as sensors in aqueous solution. The qualitative analysis of these extracts by thin-layer chromatography reveals the presence of polyphenols in the extracts that was confirmed by the determination of total polyphenols. These analyses are complemented by high-performance liquid chromatography that shows that P. granatum. L and Q. suber are rich in bioactive compounds which affect their reactions with metals. Devices based on the components of the plants reveal high sensitivity and a linear relationship with cadmium ions. The lowest measured concentrations of cadmium were 10−10 M for the pomegranate extract and 10−9 M for the acorn extract.

Voltammetric Sensor Based on a Double-Layered Molecularly Imprinted Polymer for Testosterone

ABSTRACT A novel strategy to improve the sensitivity of molecularly imprinted polymer sensors based on a double-layered molecularly imprinted polymer hybrid film-modified gold electrode was investigated for the determination of testosterone. A conductive poly(anilinomethyltriethoxysilane) film was electrodeposited on the surface of the electrode, and a molecularly imprinted polysiloxane thin film was formed on the conductive layer by a sol-gel process to enhance the electrochemical response. The performance of the sensor for testosterone was investigated by square-wave voltammetry in the presence of a hexacyanoferrate/ferrite as a redox probe. The prepared sensor provided high recognition for testosterone with a broad linear range from 10 to 100 fM and a low detection limit of 10 fM. Good sensitivity, selectivity, and stability were observed with relative standard deviations less than 5%. Good recovery of testosterone was obtained when the sensor was used for the determination of testosterone in fortified urine.