Mobility of mixture

Improved resolution and mobility of mixtures of monocylglycerols and diacylglycerols can be achieved using a chloroform-acetone solvent and borate-impregnated plates. 

Figure 15 The field dependencies of the electron mobilities of mixtures of TNF and PVK.

These investigations will obviously be developed in the frame.work of other methods sensitive to the molecular mobility of mixture components as well as the methods referred to above. 

The presence of surface conductance behind the slip plane alters the relationships between the various electrokinetic phenomena [83, 84] further complications arise in solvent mixtures [85]. Surface conductance can have a profound effect on the streaming current and electrophoretic mobility of polymer latices [86, 87]. In order to obtain an accurate interpretation of the electrostatic properties of a suspension, one must perform more than one type of electrokinetic experiment. One novel approach is to measure electrophoretic mobility and dielectric spectroscopy in a single instrument [88]. 

A reverse-phase HPLC separation is carried out using a mobile-phase mixture of 60% v/v water and 40% v/v methanol. What is the mobile phase s polarity index ... 

In general, the longer a chromatographic column, the better will be the separation of mixture components. In modem gas chromatography, columns are usually made from quartz and tend to be very long (coiled), often 10-50 m, and narrow (0.1-1.0 mm, internal diameter) — hence their common name of capillary columns. The stationary phase is coated very thinly on the whole length of the inside wall of the capillary column. Typically, the mobile gas phase flows over the stationary phase in the column at a rate of about 1-2 ml/min. 

Among the complications that can interfere with this conclusion is the possibility that the polymer becomes insoluble beyond a critical molecular weight or that the low molecular weight by-product molecules accumulate as the viscosity of the mixture increases and thereby shift some equilibrium to favor reactants. Note that we do not express reservations about the effect of increasing viscosity on the mobility of the polymer molecules themselves. Apparently it is not the migration of the center of mass of the molecule as a whole that determines the reactivity but, rather, the mobility of the chain ends which carry the reactive groups. 

In the course of mixture separation, the composition and properties of both mobile phase (MP) and stationary phase (SP) are purposefully altered by means of introduction of some active components into the MP, which are absorbed by it and then sorbed by the SP (e.g. on a silica gel layer). This procedure enables a new principle of control over chromatographic process to be implemented, which enhances the selectivity of separation. As a possible way of controlling the chromatographic system s properties in TLC, the pH of the mobile phase and sorbent surface may be changed by means of partial air replacement by ammonia (a basic gaseous component) or carbon dioxide (an acidic one). 

The reseai ch has been carried out by the liquid chromatograph Perkin-Elmer (Series 200), which has tandem detectors the diode array (X=210 nm) and the refractometer. The temperature of a column was 30 C, speed of a mobile phase is 1.5 ml/ min. As a mobile phase, mixtures of solvents methanol - water and acetonitrile - water with addition of sodium perchlorate. The columns with the modified silica gel C8 and Cl8 (4.6x220 mm, 5 pm) were used for sepai ation of the AIST and FAS components. In order to make the identification of AIST and FAS components more reliable the ratio of the values of the above-mentioned detectors signals of each substance analyzed. 

The following polyvitamin prepai ations were analyzed Kal tsid (OAO Comfort Plus , Russia), Asvitol (OAO INC Marbiofarm , Russia), Pikovit (KRKA, d.d. The New Place, Slovenia), Yeast with vitamin C (000 EKKO Plus , Russia). Chromatographic experiment has been carried out using Silufol UV-254 (Kavalier, Czech Republic) and acetone - ethyl acetate - acetic acid - ethanol (3 5 1 1) - CTAB (2T0 M) as a mobile phase mixture. The linearity calibration plot, built in coordinate S = f (IgqAC), is valid in the interval 5-25 p.g. Correctness of the determination has been checked by photometry. The obtained results for the ascorbic acid determination are presented below. 

Equation (16) was tested against some data obtained for (R) 4-phenyl-2-oxazolidinone using a range of mixtures of ethanol, acetonitrile and -hexane as the mobile phase. The column chosen was similar to that previously used for the separation of the 4-phenyl-2-oxazolidinone which was 25 cm long, 4.6 mm I.D. packed with 5 mm silica particles bonded with the stationary phase Vancomycin. The results obtained are shown in Table 1 and this is the data used in subsequent computer calculations. 

Consider the effect of the abstraction of individual solvents on consequent solute concentration. Let the volume fraction of ethanol, ethyl acetate and n-hexane in the original mobile phase mixture be (ae), (cxea) and (an), respectively. If a given solute is placed on the TLC plate at a concentration (cs) then, assuming for the... 

When prepanng mobile phase mixtures each individual component should be measured out separately and only then placed in the mixing vessel This prevents not only contamination of the solvent stock by vapors from the already partially filled mixing vessel (e g ammonia ) but also volumetnc errors caused by volume expansions or contractions on mixing... 

I) derived from this by dissociation, or in a mobile equilibrium mixture of both these forms. Dobbie et reproduced the spectra of cotarnine solutions containing varying amounts of potassium hydroxide by using cotarnine chloride and hydrocotamine and by dissolving mixtures of the latter two compounds or by placing the separate solutions of these compounds in the apparatus in series. Thus no evidence could be obtained for the occurrence of the amino-aldehyde (3) postulated by Roser. Steiner, Kitasato, and Skinner came to similar conclusions. The band at 285 m/x in alkaline solutions is not due to an aromatic aldehyde. This band also occurs in the spectrum of hydrocotamine (10a) and in the carbinolamine... 

Figure 15.4 Separation of mixtures of beta-blockers by using micellar HPLC, employing the following mobile phases (a) 0.12M SDS, 5% propanol, 0.5% tiiethylamine (b) 0.06 M SDS, 15% propanol (c) 0.1 IM SDS, 8% propanol. Adapted from Journal of Chromatographic Science, 37, S. Carda-Broch et al., Analysis of urine samples containing cardiovascular drugs by micellor liquid chromatography with fluorimetric detection , pp. 93-102, 1999, with permission from Preston Publications, a division of Preston Industries, Inc.

To maintain a high polymerization rate at high conversions, reduce the residual amount of the monomer, and eliminate the adverse process of polyacrylamide structurization, polymerization is carried out in the adiabatic mode. An increase in temperature in the reaction mixture due to the heat evolved in the process of polymerization is conductive to a reduction of the system viscosity even though the polymer concentration in it rises. In this case, the increase in flexibility and mobility of macromolecules shifts the start of the oncoming gel effect into the range of deep transformation or eliminates it completely. 

Mobility of Ions in D20. The viscosity of liquid D20 at room temperature has a value 1,232 times the viscosity of H20. Since the D2O and HaO molecules are so similar in other respects, we should expect the mobility of ions dissolved in D20 to be smaller than in H20. The conductivity of potassium chloride and potassium acetate was measured in mixtures of D20 and H20 up to a composition containing 97 per cent of D20.1 The values for ions in D2O, given in Table 7, were obtained by extrapolation from values obtained in the mixed solvent containing a few per cent of H20. As was expected, the conductivity in D20 was found to be smaller than in H20. But the change was not quite so great as the change in the viscosity, as is shown by the ratios in the last column of Table 7. We must conclude that, for some or all of the ions, the... 

The explanation for autoacceleration is as follows. As polymerisation proceeds there is an increase in the viscosity of the reaction mixture which reduces the mobility of the reacting species. Growing polymer molecules are more affected by this than either the molecules of monomer or the fragments arising from decomposition of the initiator. Hence termination reactions slow down and eventually stop, while initiation and propagation reactions still continue. Such a decrease in the rate of the termination steps thus leads to the observed increase in the overall rate of polymerisation. 

Douglas, NG Humffray, AA Pratt, HRC Stevens, GW, Electrophoretic Mobilities of Proteins and Protein Mixtures, Chemical Engineering Science 50, 743, 1995. 

Figure 6. Isotherms of the internal mobilities in 10 binary alkali nitrates. C Chemla erossing point marked only for the unelear eases. (Reprinted from M. Chemla and I. Okada, lonie Mobilities of Monovalent Cations in Molten Salt Mixtures, Electrochim. Acta 35 1761-1776, Fig. 5. Copyright 1990 with permission from Elsevier Seienee.)...

When internal mobilities of Ag are plotted against the molar volume of the mixtures, Eq. (12) seems to be applicable to AgL The internal mobilities of TF are plotted against molar volume in Fig. 12 as a compari-... 

In the alkali and alkaline earth nitrate mixtures, the internal mobilities have been systematically investigated, the isotherms being shown in Fig. 15. The internal mobilities of the alkali ions as a function of the molar volume are much smaller than expressed by an equation such as Eq. (12). This means that the internal mobilities of the alkali ions, Mju, are modified by the tranquilization effect caused by the divalent cations. The M ik is assumed to be expressed by... 

Figure 15. Isotherms of internal mobilities in alkali-alkaline earth nitrate mixtures. The mobility of the alkali ion is always greater than that of the alkaline earth ion. (Reprinted from T. Koura, H. Matsuura, and I. Okada, "A Dynamic Dissociation Model for Internal Mobilities in Molten Alkali and Alkaline Earth Nitrate Mixtures,"/ Mol. Liq. 73-75 195, Fig. 4, Copyright 1997 with permission from Elsevier Science.)...

Danek and his group have independently proposed a quite similar model, which they call the dissociation modeV - For this model Olteanu and Pavel have presented a versatile numerical method and its computing program. However, they calculated only the electrical conductivity or the molar conductivity of the mixtures, and the deviation of the internal mobilities of the constituting cations from the experimental data is consequently vague. 

The most important current problem of planar chromatography is the elaboration of theoretical and experimental methods for predicting the conditions of mixture separation in order to achieve better results. Planar chromatography is an analytical chemistry technique for the separation of mixtures that involves passing of solutes in the mobile phase through the stationary phase. Usually, each component has a... 

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