Mobility, particle

The components of a phase interface have a wide range of mobilities. The mobility of adsorbed particles exceeds that of the atoms in the bulk of a solid. It is usually considered that the mobility of the adsorbed particles is greater than that of the surface atoms of the solid, and when the state of the solid s atoms changes, the adsorbed particles at each instant are distributed practically in equilibrium. The same relation between the mobilities is presumed for absorbed particles and the atoms of a solid in the bulk. This is apparently not always true. In the general case, each component has its own ratio of the migration activation energies, and cases are possible when the mobilities of the surface atoms of a solid and of the adsorbed particles are commensurable. The mobilities of the atoms of a solid and of absorbed particles may also be commensurable. 

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Particle Mobility By equating the electrical force acting on a... 

It is interesting to note from Table XV that all methods that have been used to obtain charge distribution data by means of measurements on collections of particles at atmospheric pressure involve a measure of electrostatic particle mobility. Other aspects of charging have only been obtained with those methods in which individual particles are evaluated. 

FIGURE 6.3 Plot of column efficiency against sample mass for three neutral compounds (3-phenylpropanol, caffeine, phenol), and three charged compounds (propranolol, nortriptyline, 2-NSA [2-naphthalenesulfonic acid]) on XTerra MS (15 x 0.46 cm, 3.5 pm particles). Mobile phase acetonitrile-formic acid (overall concentration 0.02 M) pH 2.7 (28 72, v/v) except for caffeine (12.5 77.5, v/v). Flow rate 1 mL min . Column temperature 30°C. Injection volume 5 pL. 

FIGURE 6.16 Separation of 1 = phenol 2 = 2-naphthalene sulfonic acid 3 = p-xylenesulfonic acid 4 = caffeine 5 = nortriptyline 6 = diphenhydramine 7 = benzylamine 8 = procainamide on Atlantis silica column (25 x 0.46 cm, 5 xm particles). Mobile phase acetonitrile-0.1 M ammonium formate pH 3.0 (85 15, v/v), 1 mLmin b... 

Fio. 13. Chromatosnun of polystyrene additives on a 5 cm-long column packed with Spherosil/Cw, S-/im particles. Mobile phase 98 (water 40/methanol 60)/acetonitrile 2 (v/v) 1 ml/min. Inlet pressure 36 atm. Valve iitiectkm 2- 1 sample. 

Particle mobility and zeta potential can now be measured by more sophisticated techniques. With photoelectrophoresis, particle mobility is measured as a function of pH under the influence of ultraviolet radiation. At pH < 8, the electrophoretic mobility of irradiated hematite particles (A = 520 nm) was markedly different from that measured in the absence of UV irradiation. This was attributed to the development of a positive surface charge induced by photo-oxidation of the surface Fe-OH° sites to (Fe-OH) sites (Zhang et al., 1993). The electroacoustic technique involves generation of sound waves by the particles in the colloidal dispersion and from this data. 

RP-18 Column, 25 cm, 5 pm particles Mobile phase water, acetonitrile, methanol (60 20 20)... 

As it is seen in these figures, the higher n(0), the faster the asymptotics is achieved. For the immobile reactant A and d = 1, a(t) systematically exceeds that for the equal mobilities which leads to faster concentration decay in time. The results for d = 2 and 3 are qualitatively similar. Their comparison with the one-dimensional case demonstrates that the concentration decay is now much faster since the critical exponents strive for a = 3/4 and a = 1/2 for the symmetric and asymmetric cases, respectively, which differ greatly from the classical value of a = 1. Respectively, the gap between symmetric and asymmetric decay kinetics grows much faster than in the d = 1 case. Therefore, the conclusion could be drawn that the effect of the relative particle mobility is pronounced better and thus could be observed easier in t ree-dimensional computer simulations rather than in one-dimensional ones, in contrast to what was intuitively expected in [33]. 

If radiation defects are charged, their aggregation is accompanied by the internal electric fields (which are the greater, the less particle mobility and larger irradiation intensity p). Quantitative analysis of this problem has been done in [37]. (Probably, this effects has been observed experimentally in [38].)... 

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