Mercury-free sono-electroanalytical detection of lead in human blood by use of bismuth-film-modified boron-doped diamond electrodes.

We report the electroanalytical determination of lead by anodic stripping voltammetry at in-situ-formed, bismuth-film-modified, boron-doped diamond electrodes. Detection limits in 0.1 mol L(-1) nitric acid solution of 9.6 x 10(-8) mol L(-1) (0.2 ppb) and 1.1 x 10(-8) mol L(-1) (2.3 ppb) were obtained after 60 and 300 s deposition times, respectively. An acoustically assisted deposition procedure was also investigated and found to result in improved limits of detection of 2.6 x 10(-8) mol L(-1) (5.4 ppb) and 8.5 x 10(-10) mol L(-1) (0.18 ppb) for 60 and 300 s accumulation times, respectively. Furthermore, the sensitivity obtained under quiescent and insonated conditions increased from 5.5 (quiescent) to 76.7 A mol(-1) L (insonated) for 60 s accumulation and from 25.8 (quiescent) to 317.6 A mol(-1) L (insonated) for 300 s accumulation. Investigation of the use of ultrasound with diluted blood revealed detection limits of the order of 10(-8) mol L(-1) were achievable with excellent inter- and intra-reproducibility and sensitivity of 411.9 A mol(-1) L. For the first time, electroanalytical detection of lead in diluted blood is shown to be possible by use of insonated in-situ-formed bismuth-film-modified boron-doped diamond electrodes. This method is a rapid, sensitive, and non-toxic means of clinical sensing of lead in whole human blood

Electroanalytical detection of zinc in whole blood

Three different electroanalytical techniques for the determination of zinc in blood are investigated. The direct determination in diluted blood via anodic stripping voltammetry at glassy carbon and the use of Nafion-coated glassy carbon mercury electrodes are shown to lack the necessary sensitivity whereas an acoustically assisted double extraction followed by sono-ASV using a glassy carbon electrode is found to be rapid, reliable and sensitive. © 2004 Elsevier B.V. All rights reserved

Sonoelectroanalysis in acoustically emulsified media: Zinc and cadmium

Dithizone (diphenylthiocarbazone) dissolved in chloroform was employed as a ligand for the solvent extraction of either cadmium or zinc from aqueous media. Acoustic emulsification was shown to be effective both in extraction and recovery or 'back extraction' with a fresh clean aqueous solution. Quantitative analysis of cadmium or zinc removed via double sono-extraction from aqueous media hostile to voltammetric analysis proceeded via sono-square wave anodic stripping voltammetry (sono-SWASV), resulting in high sensitivity in the relatively clean medium. This technique was shown to be viable for the quantification of cadmium from surfactant containing media where direct electroanalytical techniques fail. The method was also applied to the analysis of zinc in commercial shampoo and toothpaste, giving results in close agreement with those obtained from independent analysis. Biphasic sono-extraction synergistically coupled with sono-SWASV therefore presents an attractive technique for cadmium or zinc analysis in electrode passsivating media. The technique likely removes contaminants present in the test solution since these will 'prefer' to remain in the initial aqueous phase, or will transfer to the extracting organic phase, but are unlikely to be doubly transferred into the clean final aqueous phase

Sonoelectroanalysis: investigation of bismuth-film-modified glassy carbon electrodes.

Bismuth-modified glassy carbon electrodes have been investigated for their suitability in sonoelectroanalysis. The stability of the bismuth film to the application of ultrasound was assessed via voltammetric and atomic force microscopy (AFM) studies which revealed little ablation at powers up to an intensity of 130 W cm(-2) delivered from a 25-kHz sonic horn. Furthermore, bismuth-film-modified glassy carbon electrodes were evaluated for the sonoelectroanalytical quantification of zinc and cadmium. Detection limits of 2 x 10(-7) M and 6 x 10(-9) M respectively were found after a 60-s deposition time via an acoustically assisted deposition protocol

Single walled carbon nanotubes contain residual iron oxide impurities which can dominate their electrochemical activity

We demonstrate with the electrochemical oxidation of hydrazine and the electrochemical reduction of hydrogen peroxide that residual iron impurities, likely in the form of Fe3O4, can dominate the electrochemical response of single-walled carbon nanotubes. © 2007 Elsevier B.V. All rights reserved

Electroanalytical determination of zinc in human blood facilitated by acoustically assisted double extraction

The electroanalytical determination of zinc in human blood via an acoustically assisted double extraction technique is reported. First zinc(II) is rapidly extracted from diluted blood via complexation with diphenylthiocarbazone in chloroform through acoustic emulsification of the two phases. After insonation the bulk phases reform and the metal is back extracted by emulsifying with electrochemically clean aqueous acid and the zinc quantified via anodic stripping voltammetry, giving close agreement to the blind independent AAS analysis. The double extraction method is effective since species that otherwise interfere with the direct ASV determination either remain in the initial aqueous phase, or are transferred to the organic phase, but are unlikely to be doubly transferred so producing a 'clean' final aqueous medium for ASV

Modular assembly of a preorganised, ditopic receptor for dicarboxylates.

Two types of calix[4]arene derived hosts for anions with, respectively, 1,3-alternate and cone conformations have been prepared; the 1,3-alternate system binds dicarboxylate anions in a ditopic manner while the cone compounds are deprotonated by carboxylates