Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Eluotropic series of solvents for

Table 28.1 Eluotropic Series of Solvents for Adsorbents Containing Oxygen... Table 28.1 Eluotropic Series of Solvents for Adsorbents Containing Oxygen...
Eluotropic Series of Solvents for Thin-Layer Chromatography Simion Gocan... [Pg.27]

Equation 4.13 and Equation 4.14 were tested for a series of mobile phases on alumina [29-31] and silica gel [32]. Two eluotropic series of solvent binary mixtures for alumina (a = 0.6) and silica gel (a = 0.7) have been calculated by using Equation 4.13, and the obtained data can be used to establish many such series or series of other selectivities [13,28],... [Pg.77]

As the relative elution power depends not only on the adsorbent, but in many cases on the compound types being separated, there exists no universal eluotropic series of solvent strengths. This series was given by L. R. Snyder". For another eluotropic solvent series, see J. C. Touchstone Practice of Thin-Layer Chromatography, 2 " ed., Wiley, Chichester, 1983. [Pg.495]

Materials. Origin and characteristics of the cellulose samples used are listed in Table I. The low molecular weight cellulose sample A, was prepared from American Enka rayon by hydrolysis in 4 M HCl for 15 minutes and then washed with an eluotropic series of solvents. Sheets of samples C and D were shredded in a Wiley Mill (40 mesh) before use. Sample B, with degree of polymerization DP) of 210, was used in this study except where noted. Ammonium thiocyanate (Witco Chemical) was dissolved in condensed anhydrous ammonia (Air Products). Unless otherwise noted, all chemicals were ACS reagent grade. [Pg.158]

It is well recognized that the eluotropic series of solvents, according to Snyder, is suited for monoactive site-type adsorbents, but in the case of multiactive site-type adsorbents (e.g., alumina), their imperfection becomes acute. Thus for multiactive-site-type adsorbents, the eluotropic series sequence and eluent strength values are highly dependent on the class of test solutes employed. ... [Pg.613]

A practical eluotropic series of solvents, based on the expended solubility parameter concept, was reported. This series was defined based on partial specific solubility parameter (5 ) that is equal to the sum of Keeson (5q) and acid-base (2 a b)> which represents the contribution to interaction forces introduced to characterize the solute, the mobile, and the stationary phase in liquid-solid chromatography. Exactly the same two interaction forces define e° and, consequently, there should exist a direct relation between e° and s = o+2 a b- Unfortunately, the general correlation for all the solvents on alumina is poor (r =0.75). [Pg.613]

The principle of the variation of solvent composition while holding solvent strength constant was first developed by Neher for separation of steroids. Figure 1 is a representation of the eluotropic series of Neher for application in this fashion. Six solvents, which will act as solvent Si (100% concentration, on the left), are arranged vertically, whereas the same solvents, acting as solvent S2 (100% concentration, on the right of the... [Pg.615]

Subsequent collapse of the packing can be prevented by pumping about 0.51 of solvent through at this maximum pressure level, that used later for chromatography being perfectly adequate. A silica column should be equilibrated with an eluotropic series of solvents (e.g. methanol ethyl acetate —> ferf-butyl-methyl ether —> hexane) if the slurry has been topped up with water. Finally, the column... [Pg.398]

Relative strength of the solvents on polar adsorbents arranged as an eluotropic series in ehromatographie elution strength order for pure solvents or mixtures are given in literature [13-16]. The eluotropic series of pure solvents are generally referred to a partieular adsorbent. [Pg.65]

In the mobile phase selection for the separation of compounds on thin silica gel layers, it is necessary to use not only eluotropic series based on the eluting capacity of the solvent but also eluotropic series of compounds established according to their interaction with silica gel. [Pg.75]

Table 25-2 Eluotropic series and ultraviolet cutoff wavelengths of solvents for adsorption chromatography on silica... Table 25-2 Eluotropic series and ultraviolet cutoff wavelengths of solvents for adsorption chromatography on silica...
The eluotropic series of pure solvents is generally referred to a particular adsorbent. The magnitude of the solvent strength parameter, can be defined as the adsorption energy of the solvent per unit of the standard activity surface. AU these ° values are relative to the solvent pentane, for which ° is defined equal to zero. This parameter is defined as a measure of the degree of the adsorption interaction of the solvent with the stationary phase. As a function of this magnitude, the eluotropic series for various polar adsorbents is presented in Table 1. [Pg.613]

Based on the chromatographic profiles observed on both plates, suitable binary solvent mixtures are chosen. Using another TLC plate, an eluotropic series of these solvents is prepared and tested. The start and end composition of this eluotropic series depends on the R values measured for the strongest solvent of the mixture. [Pg.149]

The calculation of r" values for a large number of binary solvents is occasionally required for gradient elution systems or for the prediction of an extended eluotropic series of binary solvents. In these cases the application of Eq. (8-10) can be tedious. Appendix III describes an approximate treatment which is essentially as accurate as Eq. (8-10), but which is much simpler and easier to apply in the case of a series of solvents A-B of varying composition. [Pg.109]

Whereas the e" values of pure solvents do not change with adsorbent activity, the relative strength of a binary solvent is a function of a [see Eq. (8-10)]. As a increases, the e" value of a binary solvent increases. For example, the experimental e value of lOvol.% benzene-pentane is 0.066 on 16% HaO-SiO . (small pore), increasing to 0.098 for 1.6% Hc O-SiOa (29). When the activity of an adsorbent is unknown, some uncertainty will exist concerning the relative strengths of a series of pure and binary solvents. Similarly, it is not possible to define an eluotropic series of both pure and binary solvents that will be precisely applicable for all adsorbent activities. [Pg.317]


See other pages where Eluotropic series of solvents for is mentioned: [Pg.227]    [Pg.730]    [Pg.731]    [Pg.732]    [Pg.735]    [Pg.157]    [Pg.227]    [Pg.730]    [Pg.731]    [Pg.732]    [Pg.735]    [Pg.157]    [Pg.79]    [Pg.231]    [Pg.494]    [Pg.732]    [Pg.157]    [Pg.64]    [Pg.74]    [Pg.563]    [Pg.191]    [Pg.127]    [Pg.70]    [Pg.178]    [Pg.100]    [Pg.335]   
See also in sourсe #XX -- [ Pg.5 , Pg.6 , Pg.23 ]




SEARCH



Eluotropic series

Eluotropic solvent series

© 2024 chempedia.info