Solvent Strength Parameters

Solvent Boiling point, °c Solvent strength parameter ... 

Solvent Boiling point, °C Solvent strength parameter Viscosity, mN s m (20°C) Refractive index (20°C) UV cutoff, nm... 

Recently, Janjic et al. published some papers [33-36] on the influence of the stationary and mobile phase composition on the solvent strength parameter e° and SP, the system parameter (SP = log xjx, where and denote the mole fractions of the modiher in the stationary and the mobile phase, respectively) in normal phase and reversed-phase column chromatography. They established a linear dependence between SP and the Snyder s solvent strength parameters e° by performing experiments with binary solvent mixtures on silica and alumina layers. 

SOLVENT STRENGTH PARAMETERS FOR SOLVENTS COMMONLY VSBD IN NORMAL PHASE TLC... 

Solvent properties, 16S-166 Solvent strength parameter, 175, 176 Solvent strength, 73 see also Eluent strength... 

In order to model the solvent strength parameters of the ODS we used the n-hexane as a model solvent due to its structural similarity with the octadecyl chains of this stationary phase. 

The most important features of this equation are the emergence of a eluotropic series, i.e., an eluent-strength series based on e°. The key solvent-strength parameter, e°, which relates to the eluotropic series, was calculated by Snyder (14) for a wide variety of pure solvents. Table 2 lists some values. 

The following table contains the common solvents used in thin-layer chromatography, with a measure of their strengths on silica gel and alumina. The solvent strength parameter, s°, is defined as the relative energy of adsorption per unit area of standard adsorbent.13 It is defined as zero on alumina when pentane is used as the solvent. This series is what was called the eluotropic series in the older literature. For convenience, the solvent viscosity is also provided. Note that the viscosity is tabulated in cP for the convenience of most users. This is equivalent to mPasec in the SI convention. Additional data on these solvents may be found in the tables on high-performance liquid chromatography. 

The strength of the solvent is defined by the solvent strength parameter, e°, as listed in Table 2.2. A solvent with a low e° is chosen, and quantities of a second solvent with a greater s° are added until the desired separation is achieved. If the desired separation does not result from altering the concentration of the second solvent, either the nature of the second solvent can be changed or another additive can be introduced. Readers are directed to Refs. 1, 6, and 7 for in-depth discussions on the development of mobile phases for normal-phase chromatography. 

The influence of the solvent in LSC is described by the solvent strength parameter °. 

The other two parameters are defined similarly the sum of the three parameters is thus normalized to 1. Values for some common solvents are listed in Table 15 (along with the Hildebrand solubility parameters and the Snyder solvent strength parameters). 

Increase in R t as a result of substituting a functional group i into the solute molecule equal to log - log Xx, where k t is for the solute substituted by i and k for the solute substituted by - H Solvent strength parameter, equal ma/An for solvent M Values of for mobile phases containing solvents B, C, or i (Eq. (28)1... 

Tables of relative solvent strengths for various adsorbents have been developed. Table 25-1 lists relative solvent strength in terms of a solvent-strength parameter for several solvents with four adsorbents, defining the adsorption energy from pentane solution to be zero. Solvent strength increases generally downward in the table.

Snyder s solvent strength parameter (see Chapter 2, section 2) (Snyder 1968, 1983)... 

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