Paper ionic mobility

The first work on pKa determination by zone electrophoresis using paper strips was described by Waldron-Edward in 1965 (15). Also, Kiso et al. in 1968 showed the relationship between pH, mobility, and p/C, using a hyperbolic tangent function (16). Unfortunately, these methods had not been widely accepted because of the manual operation and lower reproducibility of the paper electrophoresis format. The automated capillary electrophoresis (CE) instrument allows rapid and accurate pKa determination. Beckers et al. showed that thermodynamic pATt, (pATf) and absolute ionic mobility values of several monovalent weak acids were determined accurately using effective mobility and activity at two pH points (17). Cai et al. reported pKa values of two monovalent weak bases and p-aminobenzoic acid (18). Cleveland et al. established the thermodynamic pKa determination method using nonlinear regression analysis for monovalent compounds (19). We derived the general equation and applied it to multivalent compounds (20). Until then, there were many reports on pKa determination by CE for cephalosporins (21), sulfonated azo-dyes (22), ropinirole and its impurities (23), cyto-kinins (24), and so on. 

Although paper electrophoresis has been recommended for pre-testing separations before performing them on a preparative column, t.l.c. is more suitable for this purpose. Electrophoretic mobility is not strictly proportional to the extent of complex-formation it depends also on the bulk and shape of the molecule, which influence ionic mobility. In particular, bulky substituents retard the passage of the complex ion through the electrolyte. These effects have been discussed in detail.T.l.c. is also affected by the bulk of substituents but to a much lesser extent hence, it is more likely to predict the separations obtainable on a column. ... 

The first hypothesis on the conductibility of ions in electrolytic solutions and on the electrolyte dissociation of acid and basis of the young Swedish chemist Svante August Arrhenius (1859-1927) was not well accepted in his own country. He searched abroad a support for his studies and obtained it from Ostwald and Van t Hoff. He worked with them for six years between 1885 and 1891 and wrote an important paper in 1887 (Arrhenius, 1887). From thereafter his theories on ionic mobility received attention and acceptance and he won the Nobel Prize for chemistry in 1903. After the german period he returned to Sweden and studied the application of Physical chemistry to biology processes giving the basis for Biochemistry (Arrhenius, 1915). 

There are a series of papers that focus on the behavior of the radon decay products and their interactions with the indoor atmosphere. Previous studies (Goldstein and Hopke, 1983) have elucidated the mechanisms of neutralization of the Po-218 ionic species in air. Wilkening (1987) reviews the physics of small ions in the air. It now appears that the initially formed polonium ion is rapidly neutralized, but can become associated with other ions present. Reports by Jonassen (1984) and Jonassen and McLaughlin (1985) suggest that only 5 to 10% of the decay products are associated with highly mobile ions and that much of the activity is on large particles that have a bipolar charge distribution. 

Electrophoresis — Movement of charged particles (e.g., ions, colloidal particles, dispersions of suspended solid particles, emulsions of suspended immiscible liquid droplets) in an electric field. The speed depends on the size of the particle, as well as the -> viscosity, -> dielectric permittivity, and the -> ionic strength of the solution, and it is directly proportional to the applied electric field. In analytical as well as in synthetic chemistry electrophoresis has been employed to separate species based on different speeds attained in an experimental setup. In a typical setup the sample is put onto a mobile phase (dilute electrolyte solution) filled, e.g., into a capillary or soaked into a paper strip. At the ends of the strip connectors to an electrical power supply (providing voltages up to several hundred volts) are placed. Depending on their polarity and mobility the charged particles move to one of the electrodes, according to the attained speed they are sorted and separated. (See also - Tiselius, - electrophoretic effect, - zetapotential). 

Ion Diffusion in Paper. Using the "time of flight" model, it has been found that the mobility of the ionic species is approximately i orders of magnitude lower in these systems than for the case in normal aqueous systems. Based on this result, an... 

KNs. The d.c. electrical conduction of KN3 in aqueous-solution-grown crystals and pressed pellets was studied by Maycock and Pai Verneker [127]. The room-temperature conductivity was found to be approximately 10" (ohm cm) in the pure material. Numerical values for the enthalpies of migration and defect formation were calculated from ionic measurements to be 0.79 0.05 and 1.43 0.05 eV (76 and 138 kJ/mole), respectively. In a subsequent paper [128], the results were revised slightly and the fractional number of defects, the cation vacancy mobility, and the equilibrium constant for the association reaction were calculated. The incorporation of divalent barium ions in the lattice was found to enhance the conductivity in the low-temperature region. Assuming the effect of the divalent cation was to increase the number of cation vacancies, the authors concluded that the charge-carrying species is the cation, and the diffusion occurs by means of a vacancy mechanism. 

In a previous paper (11)/ we described the effects of small ionic species on the surface charge of calcium oxalate monohydrate (COM). The effects were detected by measuring the electrophoretic mobility of the particles in the aqueous phase. The influences of the activity of calcium and oxalate ions monovalent electrolytes and sulfate/ phosphate/ pyrophosphate/ and citrate ions on the electrophoretic mobility were studied. It was found that the results could be accounted for hy certain established theories for the electrical double layer/ which is also useful for analyzing the results of the present work. 

The present paper furthers the discussion of these kinSs of circuit models in two major respects. Hie first has to do with the point-to-point variations which may be expected to occur. This has been discussed to some extent by Choudhury and Patterson (19, 24). They provide a very useful parametric method which automatically adjusts the local resistances but it was not presented in a form that is easy to visualize. Hence, a reformulation of their approach will be outlined here which ties it in more closely with the more traditionally accepted "fixed resistor" analogs. The second major point has to do with extending the equivalent circuit models in such a way as to allow for additional mobile ionic species in the electrolyte. ... 

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