Microwave voltammetry

The apphed pretreatment techniques were digestion with a combination of acids in the pressurized or atmospheric mode, programmed dry ashing, microwave digestion and irradiation with thermal neutrons. The analytical methods of final determination, at least four different for each element, covered all modern plasma techniques, various AAS modes, voltammetry, instrumental and radiochemical neutron activation analysis and isotope dilution MS. Each participating laboratory was requested to make a minimum of five independent rephcate determinations of each element on at least two different bottles on different days. Moreover, a series of different steps was undertaken in order to ensure that no substantial systematic errors were left undetected. 

Electroactive 3-(N-phenylpyrazolyl)fullereno[l,2-r/]isoxazolines have been synthesized by using 1,3-dipolar cycloaddition of pyrazole nitrile oxides, generated in situ, to Cgo at elevated temperature or microwave irradiation. The cyclic voltammetry measurements show a strong donor pyrazole ring, and a better acceptor ability of the fullerene moiety than the parent C60 (538). Treating fullerene Cgo with mesitonitrile oxide in toluene gives fullerene-nitrile oxide adduct, which is supposed to be useful for electrical and optical components (539). 

Mn(II) and Fe(II) were determined by differential pulse voltammetry (9, 30). The determinations were carried out within a few hours after sampling. Total dissolved and particulate Fe and Mn (after digestion of the particulate matter in a microwave digestion unit with HN03-HC1) were measured by flame or graphite furnace atomic absorption spectrometry. 

Microwave-activated voltammetry has been applied to the ferrocyanide/ferricyanide redox couple145, reduction of Ru(NH3)g 146, enhanced Pb02 electro-deposition, stripping and electrocatalysis147 and electrodehalogenation in non-aqueous media148. 

As mentioned before, two interlaboratory studies were organised prior to certification, involving ca. 15 laboratories using techniques such as cold vapour atomic absorption spectrometry, direct current plasma atomic emission spectrometry (DCP-AES), differential pulse anodic stripping voltammetry (DPASV), microwave plasma atomic emission spectrometry (MIP-AES), electrothermal atomic absorption spectrometry (ETAAS) and neutron activation analysis with radiochemical separation (RNAA). 

Manivannan et al. used diamond electrodes to detect Pb(II) in water samples (pH = 1) by differential pulse voltammetry, measuring concentrations down to 4 nM (0.8 ppb) [57]. The preconcentration step was rather long at -1.0 V vs. SCE for 15 minutes. Prado et al. reported on the detection of Pb(II) and Cu(II) at diamond electrodes using anodic stripping voltammetry [156]. The Pb(II) was detected by both anodic- (Pb metal) and cathodic-stripping voltammetry. Pb(II) was detected in a river-water sediment sample (pH = 1) and was quantified using a standard addition method. The metal content in the sediment was found to be - 200 mg/kg by both anodic- and cathodic-stripping voltammetry. The electrode response was improved after microwave activation (e.g., thermal treatment), with a limit of detection of 21 ppb for a 20-second preconcentration time. 

ABSTRACT We report on the microwave assisted hydrothermal synthesis of LiMnPO and LiCoPO and their electrochemical characterization by means of cyclic voltammetry and potentioelectrochemical impedance spectroscopy (PEIS/SPEIS). The influence of various synthesis parameters like pH-value and reaction time on the particle shape and size and thus on the electrochemical performance are studied. In addition, effects of the battery state of charge on the impedance spectra are investigated and discussed. 

ABSTRACT Synthesis of nanostructured LiCoOj and TiO via microwave assisted and conventional hydrothermal methods, respectively, is presented. The physical properties of the resulting material are characterised via X-ray powder diffraction and scanning electron microscopy. Cyclic voltammetry and Galvanostatic Intermittent Titration Technique are used to study differences of the electrochemical properties compared to bulk material. 

Examples of stripping analyses with microwave-enhanced voltammetry are trace determination of cadmium [15-17], of lead (deposited as lead dioxide and as elemental lead) [16, 18] and of palladium [19]. 

Fig. 4.3 Arrangement for microwave-activated voltammetry. From [15], with permission...

The present chapter aims at summarizing some of the main voltammetric applications of boron-doped diamond (BDD) films, deposited on Si(lOO) wafers by means of microwave plasma-assisted chemical vapor deposition [9]. In order to put these results into better perspective, the advantages of using BDD for anodic voltammetry are correlated with the unique properties of this electrode material. In addition, analytical applications of anodic voltammetry at conductive diamond electrodes are also discussed. 

Stripping voltammetry experiments at a boron-doped diamond electrode with 2 mM Pb2+ in 0.1 M HNO3 were carried out in order to study the effect of microwave radiation on this process. Microwave activation has a considerable effect on the square-wave stripping response, with signal to noise improvements of more than one order of magnitude. 

The limit of detection by square-wave voltammetry after a 20-s deposition time was found to be 0.1 mM and 1.0 mM with and without microwave activation, respectively. The Pb content in a water sediment sample detected by anodic stripping voltammetry at boron doped diamond electrodes is shown to be in good agreement with two other independent analytical procedures based on ICP mass spectroscopy and on sono-cathodic stripping voltammetry. 

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