Search

Graphite/diamond pastes modified with 1H-pyrrole-1-hexanoic acid were used for the design of stochastic sensors. The proposed stochastic sensors were used to determine four heavy metals, copper(II)...

A simple, sensitive and selective fluorimetric method for the determination of trace amounts of nitrite in different water samples (e.g., underground water, geothermal waste water, domestic waste water and drinking water) was proposed. The fluorimetric determination is based on the diazotization reaction of nitrite with a fluorescent dye, tetraamino zinc (II) phthalocyanine in an acidic medium. Under the optimum experimental conditions, nitrite can be determined in the range 10− 6–10− 4 mol·L− 1 with the detection limit 2.04 × 10− 8 mol·L− 1. The proposed method has been successfully applied to the determination of nitrite in various water samples. The results compared favorably with the results from a standard isocertified method.

Pattern recognition of Cu(II), Pb(II), Hg(II) and Cd(II) in waste waters collected from a mining area, was performed using a fast screening method based on a new stochastic sensor. The stochastic sensor is based on physical immobilization of N,Nź-ethylenebis[N-[(3-(pyrrole-1-yl)propyl) carbamoyl) methyl]-glycine]) in diamond paste. The limits of determination of the cations were as low as 10 pmol/L [for the assay of Cd(II)], and 100 pmol/L [for the assay of Cu(II), Hg(II), and Pb(II)]. The cations were determined from the waste water samples without any pretreatment of the water samples, within 20 min with recoveries higher than 98.80 %, and low RSD (%) values.

We report the synthesis and electrochemical behavior of an original catalyst bearing a 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) unit and a pyrene group. Anchoring of this bi-functional molecule by π -stacking onto multiwalled carbon nanotubes allows the study of the electrochemical properties of the compound in the immobilized state. These resulting functionalized TEMPO materials were used to detect iron(II) in solution with an experimental detection limit of 3.9 × 10−8 mol L−1 and a linear range between 7.8 × 10−8 and 1.4 × 10−6 mol L−1. Keywords: TEMPO, Multiwalled carbon nanotubes, Pyrene, Iron(II), Electrochemical sensor

Complexing polymer-coated electrodes have been synthesized by oxidative electropolymerization of 4-azulen-1-yl-2,6-bis(2-thienyl)pyridine (monomer L). The novel chelating chemically modified electrodes were used for the electrochemical detection of Pb(II) and Cd(II) ions by means of the chemical preconcentration–anodic stripping technique. The electrode material showed a particular selectivity towards lead ions, even in the presence of a large excess of other metal cations. Detection limits of 0.7 nM and 10 nM were obtained for lead(II) and cadmium(II) ions, respectively. The modified electrodes have been used for the determination of lead in natural water and tap-water.

The electropolymerisation of N-substituted pyrroles on a dissolvable calcium carbonate nanoparticle template was investigated in order to improve the film permeabilities in aqueous solution. After deposition of CaCO3 nanoparticles on the electrode surface, poly(pyrrole-ammonium) or poly(pyrrole-NTA) (NTA: nitrilotriacetic acid) were electrogenerated around the template structures of the electrodes using potentiostatic methods. The dissolution of nanoparticles in acidic medium leads to the formation of nano-porous structures increasing, therefore, the polypyrrole permeability in aqueous solutions. Histidine-tagged glucose oxidase, chosen as an enzyme model, was immobilised on the modified polypyrrole-NTA via the NTA-Cu(2+)-histidine interactions to validate the proposed method. The described setup led to a twofold increase in the maximum current density from 5 to 10 μA cm(-2) after template dissolution.