Ternary mobile phases equation

The latter was also the case for the optimization of the composition of a ternary mobile phase in RPLC by Issaq et al. [554]. The ternary mixture was formed by mixing two limiting (non iso-eluotropic) binary mixtures and a fourth order polynomial equation was fitted through five equally spaced data points. 

In reversed-phase systems with ternary mobile phases composed of water and two organic solvents, the following simplified equation can be used to predict the dependence of the solute retention factors on the concentrations of the two oiganic. solvents, (p and tp2 [79] ... 

The mobile phase in RP chromatography contains water and one or more organic solvents, most frequently acetonitrile, methanol, tetrahyrofuran, or propanol. By the choice of the organic solvent, selective polar interactions (dipole-dipole, proton-donor, or proton-acceptor) with analytes can be either enhanced or suppressed, and the selectivity of separation can be adjusted. Binary mobile phases are usually well suited for the separation of a variety of samples, but ternary or, less often, quaternary mobile phases may offer improved selectivity for some difficult separations. The retention times are controlled by the concentration of the organic solvent in the aqueous-organic mobile phase. Equation 1 is widely used to describe the effect of the volume fraction of methanol or acetonitrile

[Pg.1440]

Although the quadratic equations for retention (In k) as a function of mobile phase composition (experimental data, they are inadequate to describe retention within experimental error. For binary mixtures the standard deviation between the quadratic equation (eqn.3.38) and experimental data is typically between 5 and 10% (depending on the solute) [322], For ternary systems average deviations of 10 to 20% are typical [324]. However, the inclusion of additional (higher order) terms at will is not an attractive way to improve the description of the experimental data. We will discuss this more fully in chapter 5 (section 5.5). 

In ternary organic mobile phases with a constant concentration ratio of two solvents with great elution strengths, (px/tpi, the sum of the two concentrations, tpx =

retention behaviour in normal-phase ternary solvent systems often can be described by the equation formally identical with Eq. (1.15) [27,80], as is illustrated by Fig. 1.20 ... 

Ternary Gradient Systems. While the fitting of the Isocratlc concentration vs retention relationship Is fairly straightforward for mobile phases containing one modifier. It becomes Increasingly difficult as the number of modifiers Increases. Ternary solvent systems contain two Independent and one dependent variables and require at least six Isocratlc data points to fit to Equation 2. 

A 128 X 64 X 16 finite element model in three dimensions was established to investigate the composition profile the physical dimensions of the slab before nondimensionaUzation are listed in Table 15.4. The numerical simulation was conducted based on the experimental conditions. Some of the parameters were directly imported from the experimental condition, while some - such as the gradient energy coefficient and mobility - were difficult to measure. Those parameter values which were not directly obtainable were first estimated via the theories described in Section 15.4.2, and then benchmarked in the numerical simulation with the experimental results. For phase separation in a polymer-polymer-solvent ternary system, the solubility of the polymers in the solvent is much greater than that of the polymers in each other [94]. Consequently, the interaction parameters between the solvent and two polymers were set as 0, and the interaction parameter between two polymers can be estimated with the following equation [33] ... 

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