Column equilibration, displacement

FIG. 16-30 Operational steps in displacement chromatography, The column, initially equilibrated with a carrier solvent at time 0, is loaded with feed until time tp and supplied with displacer for a time to + tp. Development of the displacement train occurs during the time to and elution of the separated products ends at time tp. tp is the time required to remove the displacer from the column and restore the initial conditions, Components are niimhered in order of decreasing affinity for the stationary phase, [Reference Horoath et at, J, Ghromatogr, 2i8, 365 (1981). Reprinted with peimission of], Ghromatogr,]... 

We have found that similar behavior occurs when the column is packed with other salts of Group I elements, such as NaSbF Na AlF, or NiF, or with Nafion ion-exchange resins (H or K forms). In batch equilibration experiments, using 1 g amounts of solids stirred with 5-15 ml volumes of solutions, we have found that the radon ions can also be collected on the compounds CsBrF, Ca(BrF )2, and Ba(BrF )2. Thus it is apparent that, in its oxidized state, radon can displace H, Na, K, Cs, Caz, and Baz ions from a number of solid materials. 

Estimation of adsorption isotherms, the search for an appropriate displacer, scale-up, and optimization of the method with an analytical column will be described elsewhere [84]. The result of this development report can be summarized as follows. After equilibration of the reversed-phase column... 

Displacement chromatography is characterized by the introduction of a discrete volume of sample into the chromatographic column that has been previously equilibrated with a weak mobile phase, termed the carrier. This carrier is chosen so that the individual components of the sample (the solutes) are significantly retained by the stationary phase. The displacement is accomplished by following the sample with a new mobile phase containing some concentration of the displacer, a molecule with a higher affinity for the stationary phase than that of any of the solutes. The solutes are displaced from the stationary phase by the higher-... 

The column is equilibrated with the carrier mobile phase (I), and the injection of a sample (F) of a binary mixture (components A and A2) is performed diu-ing a finite period of time (tq — utj,J L), after which the displacer (P3) stream is pumped into the column. There are two concentration shocks one at the origin (0, 0), the stable front shock of the first component, the other at the end of the injection (0, To), the front shock of the displacer. Thus, two wave solutions appear in the x, t) plane. According to Eq. 9.25, for an initially empty bed, the characteristic parameters are I ai,a2, cif). State F represents the injection of A and A2 into the column according to Eq. 9.26, the characteristic parameters are F(co, ui2,as), where... 

As an eluent is pumped through a column, the resin becomes equilibrated with the eluent. The desired process is an ion-exchange equilibrium in which the anions on the resin are displaced by the eluent anion. However, a second equilibrium process can occur in which the molecular form of the eluent is sorbed by the resin matrix. A system peak results from a change in this latter equilibrium which is caused by injection of a sample. If the sample pH is more basic than the eluent, then part of the sorbed eluent is ionized and desorbed. The system peak which elutes later is from the readsorption of the eluent hence, in this case it is a decreasing peak of dip. If the sample... 

The column generator (and related HPLC) method of determining aqueous solubility has become the predominant method in the literature over the past 5 years. In this method, a column is packed with an inert solid support which provides a high surface area for the solute to insure quick equilibration between it and the aqueous phase. After the support is impregnated with the solute of interest and excess solute has been displaced, the column is brought to the desired temperature and the aqueous concentration is determined as a function of flow rate. The equilibrium concentration corresponds to the highest eluting flow rate where solute concentration remains flow-independent. 

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