Stationary phases mixtures

Vs) is the total volume of stationary phase in the column and (a) is the volume fraction of phase (A) in the stationary phase mixture... 

Now, if the solutes interact with themselves more strongly than they do with the stationary phase, then their presence will increase the interaction of further solute with the stationary phase mixture. This gives an isotherm having the shape shown in Figure 10. This type of isotherm is called a Freundlich isotherm, the expression for... 

Predicting Retention for Binary Stationary Phase Mixtures... 

Figure 3.3 Variation of retention (distribution coefficient) with the composition of the stationary phase in GLC at three different temperatures (indicated in the figure in °C). Stationary phase mixtures of squalane and dinonylphthalate (DNP). Solutes (a) n-octane, (b) cyclohexane, (c) methylcyclohexane and (d) tetrahydrofuran. Straight lines observe eqn.(3.14). Figure taken from ref. [304]. Reprinted with permission. 

Figure 5.1 One-dimensional response surface for the optimization of the stationary phase composition in gas chromatography. Horizontal axis composition of binary stationary phase mixture. Vertical axis lowest value for a(amin) observed in the chromatogram. For further explanation see section 5.5.1. Figure taken from ref. [501]. Reprinted with permission.

Optimization of the selectivity in programmed temperature GC requires the application of different stationary phases or stationary phase mixtures. 

The retention ratio of a pair of enantiomers increases steadily with the amount of cyclodextrin in the stationary phase mixture. This increase tends to flatten above 15%. The effect of temperature is even more interesting and it is clearly seen that temperature is a major factor controlling selectivity. Reducing the operating temperature from 100°C... 

Key L = ligand (5-chloro-2,3-dihydroxypyridine). Stationary phase Mixture of silica gel G and p-toludine (50 1, w/w). Mobile phase M, = Acetonitrile M2 = methanol M3 = acetonitrile-methanol (1 1). Detection Self colored complexes vizualized on chromatoplate with the help of UV-visible lamp. Conditions Ascending technique, layer thickness 0.5 mm, drying of plates at 40°C for 24 h., run 11 cm, development time 30-40 min. Remarks The values are in the order of Co > Fe > Mn > Cr. Reversed phase HPLC separation of the complexes was also carried out on Zorbax ODS column with acetonitrile-methanol-water (6 1 3) eluent using UV-visible detector. 

Key L = ligand (S-chloro-2,3-dihydroxypyridine). Stationary phase Mixture of silica gel C and p-toludine (50 1, w/w). Mobile phase = Acetonitrile =... 

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