Molecularly imprinted polymer modified glassy carbon electrodes for the electrochemical analysis of isoproturon in water.

Isoproturon-imprinted polypyrrole films were electrochemically synthesized onto glassy carbon (GC) electrodes in an ethanol/aqueous solution of pyrrole as a monomer, isoproturon as a template molecule and LiClO4 as supporting electrolyte. Electropolymerization was performed by cyclic voltammetry and chronoamperometry. The isoproturon template molecules were successfully trapped in the polypyrrole film where they created artificial recognition cavities. After the electrochemical extraction of the template, the polypyrrole film acted as a molecularly imprinted polymer (MIP) for the selective recognition of isoproturon whereas the non-imprinted polymer (NIP) film, made in the same conditions except for the presence of isoproturon, did not exhibit any interaction. The MIP and NIP films were characterized by cyclic voltammetry in the presence of redox probes and the thickness of the polymer layers was estimated by EQCM (Electrochemical Quartz Crystal Microbalance) and calculated using Faraday's law. The isoproturon-imprinted polypyrrole films were found to selectively detect isoproturon even in the presence of the interferents carbendazim and carbamazepine. Its limit of detection (LOD) in milli Q water, achieved via square wave voltammetry was as low as 0.5 µg L-1, whereas in real water samples it was found to be 2.2 µg L-1.

Trace lead analysis based on carbon-screen-printed-electrodes modified via 4-carboxy-phenyl diazonium salt electroreduction.

This paper describes the use of 4-carboxyphenyl-grafted screen-printed carbon electrodes (4-CP-SPEs) for trace lead analysis. These novel and simple use of electrodes were easily prepared by the electrochemical reduction of the corresponding diazonium salt. Pb detection was then performed by a three-steps method in order to avoid oxygen interference: (i) immersion of the grafted screen-printed electrode (SPE) in the sample and adsorption of Pb(II), (ii) reduction of adsorbed Pb(II) by chronoamperometry (CA), and (iii) oxidation of Pb by Anodic Square Wave Voltammetry (SWV). The reoxidation response was exploited for lead detection and quantification. In order to optimize the analytical responses, the influence of the adsorption medium pH and the adsorption time were investigated. Moreover, an interference study was carried out with Cu(II), Hg(II), Al(III), Mn(II), Zn(II), Cd(II) and no major interference can be expected to quantify Pb(II). The described method provided a limit of detection and a limit of quantification of 1.2 × 10(-9)M and 4.1 × 10(-9)M, respectively. These performances indicate that the 4-CP-SPE could be considered as an efficient tool for environmental analysis.

Screen-printed electrografted electrode for trace uranium analysis.

This paper reports the interest of the novel 4-carboxyphenyl-grafted screen-printed electrodes (4-CP-SPEs) for sub-nanomolar analysis of uranium in water samples. Electrodes were easily prepared via electrochemically reduction of the corresponding diazonium salt. The stability of the grafted layer has been clearly demonstrated. Uranium detection was then achieved by immersing the grafted electrode into the sample solution, followed by the electrochemical measurement of adsorbed U(VI) by square wave voltammetry. Adsorption time was investigated so as to find the best compromise between analysis time, repeatability and reproducibility. Limit of detection and quantitation reached 7 x 10(-10) and 2 x 10(-9) mol L(-1), respectively. Moreover, interference study was conducted with Zn(II), Cd(II), Pb(II) and Cu(II); no major interference was established. 4-CP-SPEs were finally applied for uranium determination in estuarine water demonstrating the convenience of these electrodes for environmental analysis.