Electroanalytical determination, elemental

Ultrafiltration was applied to examine the size fractionation of Al, Ca, Cu, Fe, K, Na, and Pb in white and red wines [91]. Metal determinations were performed on the unfiltered wine, the 0.45 p,m membrane-filtered wine and each ultrafiltrate fraction. Aluminum was determined by ET-AAS, while FAAS was employed for Cu and Fe. An electroanalytical technique, stripping potentiometry, was selected for Pb measurement, whereas flame photometry was chosen for K and Na quantification. Fractionation patterns were evaluated and discussed. Castineira et al. [92] combined on-line tangential-flow multistage ultrafiltration with a home-built carbon analyzer and ICP-MS for size fractionation of nonvolatile dissolved organic compounds and metal species in three German white wines. The study showed that the major part of the elements investigated (up to 25) were dissolved in the size fraction of < 1 kDa, with the exception of Ba, Pb, and Sr, which also appeared in other fractions. 

Frenzel W, Bratter P (1987) Applications of electroanalytical flow analysis in the trace element determination of biological materials. In Bratter P, Schramel P (eds) Trace element analytical chemistry in medicine and biology. Walter de Gruyter, Berlin, p 337 van den Berg CMG (1999) Determination of trace elements. Analysis by electrochemical methods. In Grasshoff K, Kremling K, Ehrhardt M (eds) Methods of seawater analysis. Wiley-VCH, Weinheim, p 302 Kalvoda R (2000) Crit Rev Anal Chem 30 31 Mart L (1979) Fresenius Z Anal Chem 296 350 Barek J, Mejstfik V, Muck A, Zima J (2000) Crit Rev Anal Chem 30 37... 

Atomic spectrometric techniques such as flame atomic absorption spectrometry (FAAS), electrothermal AAS (ETAAS), inductively coupled plasma atomic emission spectrometry (ICP-AES), and ICP-MS are used for the determination of elements, particularly metals. ICP-MS is the most sensitive, typically with microgram per liter detection limits and multielement capability but it has high start-up and operating costs. UV-visible spectrophotometry is also used for the determination of metal ions and anions such as nitrate and phosphate (usually by selective deriva-tization). It is a low cost and straightforward technique, and portable (handheld) instruments are available for field deployment. Flow injection (FI) provides a highly reproducible means of manipulating solution chemistry in a contamination free environment, and is often used for sample manipulation, e.g., derivatization, dilution, preconcentration and matrix removal, in conjunction with spectrometric detection. Electroanalytical techniques, particularly voltammetry and ion-selective electrodes (ISEs), are... 

Anodic stripping voltammetry, potentiometric stripping voltametry, and differential pulse polarography are used for the simultaneous determination of up to 10 analytes at extremely low concentrations (detection limits <0.01 pgl ). Electroanalytical techniques are applicable for 30 elements. Stripping analysis allows differentiation between chemical forms but is subject to interference from adsorption... 

Other analytical techniques. Electroanalytical methods can also be used to differentiate between ionic species (based on valence state) of the same element by selective reduction or oxidization. In brief, the electroanalytical methods measure the effect of the presence of analyte ions on the potential or current in a cell containing electrodes. The three main types are potentiometry, where the voltage difference between two electrodes is determined, coulometry, which measures the current in the cell over time, and voltammetry, which shows the changes in the cell current when the electric potential is varied (current-voltage diagrams). In a recent review article, 43 different EA methods for measuring uranium were mentioned and that literature survey found 28 voltammetric, 25 potentiometric, 5 capillary electrophoresis, and 3 polarographic methods (Shrivastava et al. 2013). Some specific methods will be discussed in detail in the relevant chapters of this tome. 

Nanoelectrode ensembles (NEEs) (see also Chapter 10 of this handbook) are nanotech-based electroanalytical tools which find application in a variety of fields ranging from electroanalysis to sensors (86) and electronics (7). They are fabricated by growing metal nanowires in the pores of a template, typically a PC nanoporous manbrane. The density of the pores in the template determines the number of Au-disk nanoelectrode elanents per cm of NEE surface and, correspondingly, the average distance between the nanoelectrode elements. Such electrode systems proved to be valuable tools for trace determinations and kinetics studies by simply using cyclic voltammetry (CV) (5, 69, 86, 97). 

As summarised in Table 3.4, some electroanalytical methods have been certified by standardisation bodies for the chemical characterisation of ambient water samples, mostly in the class of inorganic substances. Conductometric detection is used in direct method for ionic constituents and also as chromatographic detector for individual cations and anions. Total, inorganic and organic carbon in water can be also assayed by conductometric detection. Amperometric detection has been certified for dissolved oxygen and cyanide. ISE potentiometry is used for standardised measurements of a set of ions and also for the evaluation of water oxidation-reduction potential. Voltammetric detection is the base for diverse methodologies oriented to the determination of trace elements including the most relevant elemental pollutants. 

In Table 5.2, a selected overview of typical electroanalytical methods for the determination of the above-stated elements is given. ... 

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