Simultaneous electrochemical DNA hybridization assay for PAT and FMV 35S gene sequence using quantum dots as labels

An electrochemical method for the simultaneous detection of two different DNA sequences from PAT and FMV 35S gene sequence using CdS and PbS quantum dots （QDs） as labels was described. The QDs were readily functionalized with oligonucleotides as electrochemical DNA probes and selectively hybridized to the complementary sequences immobilized on the microplate. The QDs anchored on the hybrids were dissolved in the solution by the oxidation of HNO3 and further detected by a sensitive differential pulse anodic stripping voltammetric method （DPASV）. The DPASV signals of the oxidation of Cd^2＋ and Pb^2＋ ions present in the solution were different and reflected the identity of corresponding ssDNA targets sequences.

Automated Determination of Cd^(2+) and Pb^(2+) in Natural Waters with Sequential Injection Analysis Device Using Differential Pulse Anodic Stripping Voltammetry

An electrochemical flow device has been developed for the determination of heavy metal ions(HMI)in water using multiwalled carbon nanotubes(MWCNTs)/Nafion(NA)/Hg electrode,by mean of diff erential pulse anodic stripping voltammetry coupled with sequential injection analysis.The accuracy of the determination was ensured by the great electrical conductivity of MWCNTs and the high adsorption capacity of Hg.NA was used for MWCNTs immobilization for the long-term application of the electrode.The mercury film was cleaned after determination and another one would form during deposition.A lower limit of detection and a wider determination range of Cd^(2+)and Pb^(2+)could be achieved using the automatically analytical device combining with the MWCNTs/NA/Hg-modified electrode.The real-time monitoring of Cd^(2+)and Pb^(2+)in fresh water using this device continued for 10 days.The results indicated that the method was potential for on-site and real-time determination of HMI in water samples.

Differential Pulse Anodic Stripping Voltammetric Determination of Lead with Heparin Modified Electrode

A novel differential pulse anodic stripping voltammetry for the determination of trace amounts of lead, using a biomacromolecule heparin drop-coated modified glassy carbon electrode, has been described. Pb2+ was deposited on the surface of a heparin-modified electrode at -1.0 V (vs. SCE) via forming Pb2+-heparin and subsequent re-duction at the electrode. In the following step, Pb-heparin was oxidized, and voltammograms were recorded by scanning the potential in a positive direction. Conditions were optimized with respect to the pH of the medium, the mass of drop-coated heparin, accumulation potential and accumulation time. The peak current was proportional to the Pb2+ concentration in the range of 2.0×10-9 to 7.0×10-7 mol/L. The detection limit was 3.0×10-10 mol/L. The relative standard deviation was 4.83% for 1.0×10-8 mol / L Pb2+ (n=10). The developed method has been applied to the determination of Pb2+ in water samples with satisfactory results.

A voltammetric sensor for simultaneous determination of lead,cadmium and zinc on an activated carbon fiber rod

In this work, a simple, low cost and sensitive voltammetric sensor was developed for the simultaneous detection of lead （Pb2＋）, cadmium （Cd2＋）, and zinc （Zn2＋） ions based on a disposable carbon fiber rod （CFR）. The important factors to enhance the sensing property were creation of a clean surface by dealing with CFR at a high potential and electrochemical deposition of bismuth （Bi） film to improve the accumulation of heavy metal ions. The morphology and conductivity of such activated CFR was characterized by scanning electron microscopy and electrochemical impedance spectroscopy, respectively. In terms of application, differential pulse anodic stripping voltammetry （DPASV） was employed for the simultaneous detection of Pb2＋, Cd2＋, and Zn2＋ on Bi film-coated activated CFR. Experimental parameters, such as the pH value of buffer solution, stirring speed and enrichment factors were optimized. Under optimal conditions, the DPASV peak currents showed good linear relationships with Pb2＋, Cd2＋ and Zn2＋ concentrations in the range of 0.5-2.25 μg/L, 0.5-4.0 μg/L and 1.0- 4.0 μg/L with detection limits of 0.1, 0.3 and 1.0 μg/L （SIN = 3）, respectively. Finally, the proposed analysis system was successfully utilized for the simultaneous detection of Pb2＋, Cd2＋, and Zn2＋ contents in rice samples. This study indicated that Bi film-coated activated CFR based DPASV sensor can be a promising and reliable tool for rapid analysis of emergency Dollution affairs of heavv metal ions in food.