Tarso B. Ledur Kist - Open and Toroidal Electrophoresis

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Open and Toroidal Electrophoresis: краткое содержание, описание и аннотация

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Presents the theory and applications of Toroidal Capillary, Microchip, and Slab Electrophoresis to analytical chemists across a range of disciplines Written by one of the developers of Toroidal Capillary Electrophoresis (TCE), this book is the first to present this novel analytical technique, in detail, to the field of analytical chemistry.
The exact expressions of separation efficiency, resolution, peak capacity, and many other performance indicators of the open and toroidal layouts are presented and compared.
Featuring numerous illustrations throughout,
offers chapters covering: Solvents and Buffer Solutions; Fundamentals of Electrophoresis; Open Layout; and Toroidal Layout. Confronting Performance Indicators is next, followed by chapters on High Voltage Modules and Distributors; Heat Removal and Temperature Control; and Detectors. The book finishes with an examination of the applications of Toroidal Electrophoresis.
The first book to offer a detailed account of Toroidal Electrophoresis—written by one of its creators
Compares the toroidal layouts with the well-established open layouts of the three most used platforms (Capillary, Microchip, and Slab) Provides solutions to many of the experimental issues arising in electromigration techniques and discusses the voltage distributors and detectors that are compatible with the toroidal layouts Richly illustrated with a large number of useful equations showing the relationships between important operational parameters and the performance indicators 
is aimed at method developers and separation scientists working in clinical analysis, and food analysis, as well as those in pharmacology, disease biomarker applications, and nucleic acid analysis using the Capillary, Microchip, or slab Platform. It will also benefit undergraduate and graduate students of inorganic analytical chemistry, organic analytical chemistry, bioanalysis, pharmaceutical sciences, clinical sciences, and food analysis.

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1.1.5 Dissociation

Ionic liquids and ionic solids are predominantly made by cations and anions that are held together by electrostatic attraction. This is the state of salts and even some bases and acids. They tend to stay in this state when mixed with most solvents at room temperature. The thermal motion of the solvent molecules, even at room temperature, continuously pushes ions from the edges and corners of these ionic solutes due to inelastic collisions. In most solvents the electric restoring force, given by equation 1.1, pulls the the ions back. Within water, however, two things happen:

1 The detached ions are immediately subjected to solvation

2 The restoring force is much weaker because the relative permittivity () of water is very high ( equation 1.1).

These two properties of water make it a very good solvent for the dissociation of ionic liquids or ionic solids at room temperature.

As well as looking at the forces involved, another way to understand the unique ability of water to dissociate ionic liquids and solids is to examine the energies involved. Again, suppose that an ion is momentarily separated by thermal energy from a vertex or edge of a small neutral crystal stone of a solute. The detached ion is then immediately solvated and is initially positioned at distance картинка 73, in close contact with the crystal. The energy necessary to move this ion from this position ( картинка 74) to infinity is found by replacing картинка 75by картинка 76in equation 1.1and integrating it over Open and Toroidal Electrophoresis - изображение 77, from Open and Toroidal Electrophoresis - изображение 78to infinity. The result is given by:

(1.2) Open and Toroidal Electrophoresis - изображение 79

This is the energy necessary to move the ion with charge картинка 80, and the resulting oppositely charged small crystal with charge картинка 81from картинка 82to infinity. From Table 1.1is possible to see that in water this required energy is 10 times smaller than what would be necessary, for instance, to perform the same operation in tetrahydrofuran, which has a relative permittivity of 7.6. All of this was calculated without counting the solvation phenomena, which favors water over most other solvents. In conclusion, both the electric forces among ions and the electrostatic energy change, which occurs when separating these ions from each other, is much smaller inside water than most of the solvents that are liquid at room temperature and one atmosphere of pressure.

Therefore, a large quantity of ionic liquids and ionic solids, with molecular formula are subjected to dissolution via a dissociation reaction when mixed in water - фото 83, are subjected to dissolution via a dissociation reaction when mixed in water. At the saturation point the following equilibrium is observed:

The maximum solubility of ionic liquids and ionic solids is an important - фото 84

The maximum solubility of ionic liquids and ionic solids is an important parameter in practical preparative and analytical applications of ESTs. For instance, some analytes are not soluble above certain concentrations, which must be known to avoid errors in the analysis. The same is true for buffers within certain temperature ranges. The maximum solubilities of analytes and buffers at a given temperature are tabulated in the literature and are usually expressed in grams per 100 milliliters of solution.

Another way to express maximum solubility is the so-called solubility product , which is defined as Open and Toroidal Electrophoresis - изображение 85. This is also well recorded in the literature and is very useful for the theoretical modeling of problems in inorganic chemistry.

The above paragraphs merely give qualitative discussions of the phenomena involved in dissociation reactions. Gibbs free energy change can actually be used to accurately predict if a reaction (dissolution with dissociation) may occur or not (see Section 1.1.8). It is fair to make a clear distinction between dissociation and ionization. The so-called ionic substances (liquids or solids) are predominantly in the form of cations and anions. Therefore, their solubilization in water is merely dissolution with dissociation. On the other hand, a large number of substances are predominantly in the form of covalent liquids, solids, or even gases. Only when placed in water (and a few other solvents) do they ionize to the form of cations and anions. In this case the process is better called dissolution by ionization.

1.1.6 Ionization

Water molecules constantly collide with each other inside pure liquid water. In some collisions a proton of one water molecule attaches to the sp 3non-bonding orbital of a second water molecule, as given by: 2H 2O → H 3O ++ OH −. The generated ions (hydron and hydroxyl) are then immediately solvated and in a fraction of the events the solvated ions move apart as a cation (H 3O +) and an anion (OH −), driven by thermal energy and facilitated by the low restoring force, which occurs because of the high relative permittivity картинка 86of bulk water ( equation 1.1). At a given temperature there is a constant rate of ion production and recombination (H 3O ++ OH −→ 2H 2O), which leads to an equilibrium denoted by:

(1.3) This phenomenon is the so called selfionization of water ie water itself - фото 87

This phenomenon is the so called self-ionization of water , i.e. water itself undergoes ionization due to its remarkable properties ( water falls victim to itself ). Moreover, this reaction shows the amphiprotic nature of water, as it possesses both the characteristics of a Brønsted acid and base.

Molecules carrying acidic and basic functional groups are also subjected to ionization when introduced into water. For carboxylic acids (e.g., formic acid) there are at least two possible reactions for their ionization:

(1.4) 15 where the source of the OH ions is the selfionization of water These - фото 88

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