Metrics, electrochemical

The correlation between the electrochemical transients observed on planar electrodes and superconformal film growth in sub-micrometer features indicates that the electrochemical metrics can be used for rapid screening of potential superfilling electrolytes. A more detailed and focused discussion of measurements and modeling of the SPS-PEG-C1 additive system for copper plating follows with the notion that the approach used is directly applicable to many other systems. 

Potential and Concentration—The Nernst Equation The potential of a potentio-metric electrochemical cell is given as... 

Economic Aspects. U.S. capacity for production of merchant sodium dithionite (soHds basis) was estimated at 93,000 metric tons in 1994. There are three North American producers of sodium dithionite. Hoechst Celanese is the largest producer (68,000 tons capacity) with two formate production locations and one zinc process location. Olin (25,000 t capacity) produces solution product only at two locations using both the amalgam and electrochemical processes. In 1994, Vulcan started a small solution plant in Wisconsin using the Olin electrochemical process. In addition, it is estimated that 13,000 t/yr is produced at U.S. pulp mills using the Borol process from sulfur dioxide and sodium borohydride. Growth is estimated at 2—3%/yr. The... 

Chlorobenzenes were first synthesized around the middle of the nineteenth century the first direct chlorination of benzene was reported in 1905 (1). Commercial production was begun in 1909 by the former United Alkali Co. in England (2). In 1915, the Hooker Electrochemical Co. at Niagara EaUs, New York, brought on stream its first chlorobenzenes plant in the United States with a capacity of about 8200 metric tons per year. 

Test method for sandwich corrosion test Recommended practice for preparing, cleaning, and evaluating corrosion test specimens Practice for aqueous corrosion testing of samples of zirconium and zirconium alloys Test method for corrosion testing of products of zirconium, hafnium and their alloys in water at 633 K or in steam at 673 K [metric] Recommended practice for conventions applicable to electrochemical measurements in corrosion testing... 

Recent ECQM work and X-ray diffraction have confirmed the conversion of the a/y cycle to the / // cycle up on electrochemical cycling in concentrated alkali. Earlier ECQM studies of a- Ni(OH)2 films had shown a mass inversion in the microgravi metric curve after prolonged cycling [64] there is a mass decrease in charge instead of a mass increase. More recent work has confirmed that this mass... 

Figure 6. Simplified scheme showing the stage formation during electrochemical formation of lithiated graphite. Left schematic galvanosta-tic curve. Right schematic voltam-metric curve. Prepared with data from 192, 100, 104, 105, 110], For a more detailed discussion, see text.

Depending on their conversion efficiency, electrochemical detectors can be divided into two categories those that electrolyze only a negligible fraction (0.1-5%) of the electroactive species passing through the detector (amperometric detectors), and those for which the conversion efficiency approaches 100% (coulo-metric detectors). Unfortunately, the increased conversion efficiency of the analyte is accompanied by a similar increase for the electrolyte (background) reactions, and no lowering of detection limits is reahzed. 

Complement induced immune lysis of cells and liposomes to release markers which are then detected electrochemically has been used to detect antibodies and antigens in a homogeneous format at nanomolar levels 252-256) qqjJj amperometric and potentio-metric electrodes have been employed. Unfortunately, major improvements in sensitivity appear unlikely, and instability of liposomes makes development of stable reagents for commercial systems difficult. 

In scanning electrochemical microscopy (SECM) a microelectrode probe (tip) is used to examine solid-liquid and liquid-liquid interfaces. SECM can provide information about the chemical nature, reactivity, and topography of phase boundaries. The earlier SECM experiments employed microdisk metal electrodes as amperometric probes [29]. This limited the applicability of the SECM to studies of processes involving electroactive (i.e., either oxidizable or reducible) species. One can apply SECM to studies of processes involving electroinactive species by using potentiometric tips [36]. However, potentio-metric tips are suitable only for collection mode measurements, whereas the amperometric feedback mode has been used for most quantitative SECM applications. 

Electrochemical detectors that measure current associated with the oxidation or reduction of solutes are called amperometric or coulo-metric detectors. The term ec detector normally refers to these types rather than conductivity detectors. 

Electrolytic cells. When a potential difference is applied across two electrodes that dip into a solution, a current will flow between them (Figure 4.1). The amount of current that flows depends upon the voltage applied and the electrochemical properties of the solutions. This provides the basis for conductimetric and polarographic methods of analysis. In a similar manner, the total amount of chemical change which takes place at an electrode is related to the total amount of current. This forms the basis of coulo-metric methods of analysis. 

Electrochemical biosensors are the most common especially when the biological component is an enzyme. Many enzyme reactions involve electroactive species being either consumed or generated and can be monitored by ampero-metric, potentiometric or conductimetric techniques, although the latter are the least developed and will not be discussed further. 

Without any doubt, cyclic voltammetry is the most popular voltam-metric technique used in the field of inorganic chemistry. Unfortunately, the power of the technique is frequently overestimated in that simple cyclic voltammetric measurements rarely allow one to gain complete electrochemical information. As we will discuss, it must be always coupled with complementary techniques. 

There are two basic approaches used to characterize seawater DOM (Benner, 2002). The first of these is to directly analyze bulk compositions (e.g., elemental or isotopic compositions) or individual compounds in the sample without concentration. This approach requires high-sensitivity methods for either broad biochemical types (e.g., total amino acids or carbohydrates) or individual compounds, often by either spectroscopic or chromatographic methods coupled to electrochemical or mass spectro-metric detectors. The latter type of molecular-level analyses are now feasible for measuring individual amino acids (Lindroth and Mopper, 1979), sugars (Skoog et al., 1999), and amino sugars (Kaiser and Benner,... 

Perhaps the best-known and most widely appreciated electrochemical transformation is the Kolbe oxidation (see also Chapter 6) [1, 2, 31]. The process involves the one electron oxidation of the salt of a carboxylic acid, and the loss of carbon dioxide to afford a radical, R, that subsequently engages in coupling reactions. Both symmetrical (R + R ) and nonsym-metrical (R + R ) radical couplings are known and are illustrated in the following discussion. The nonsymmetrical variety (often referred to as a mixed or hetero coupling) is remarkable given that it requires the cogeneration and reaction of more than one reactive intermediate. 

The peptide fragments of metalloth-ioneins Lys-Cys-Thr-Cys-Cys-Ala [56-61] (FT) were studied by different electrochemical techniques. The cyclic voltam-metric behavior of the peptide fragment in the presence of Cd(II) indicated two reversible electrochemical processes due to the oxidation of the mercury electrode in the presence of CdFT and reduction of CdFT complex, both from the dissolved and adsorbed state [105]. The influence of the experimental conditions on electroreduction of Cd-metallothioneins... 

A series of papers have been devoted to the silver deposition on single-crystal surfaces of other metals, mainly Au(lll) and Au(lOO). Zell etal. [303] have performed electrochemical in situ STM, cyclic voltam-metric, and potential-step studies of phase formation during Ag (and Al) electrodeposition from the room-temperature molten... 

Gopinath et al. describe the reduction of U(VI) to U(IV) at an activated platinum electrode in 1 M H2SO4 for the coulo-metric determination of uranium [63]. The platinum working electrode is chemically and electrochemically oxidized and then electrochemically reduced to produce a surface that is more active toward uranium... 

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