Separation displacement

Displacement Separations of More Complex Protein Mixtures.315... 

Displacement Separations oe More Complex Protein Mixtures... 

FIGURE 11.6 Displacement separation of rHnBDNF feedstock. Loading was 20mg/mL on a4.6x500mm column of POROS HS/M resin. (Reprinted with permission from Elsevier from Zhao, G.F. and Sun, Y., 7. Chromatogr., 1165, 109, 2007. Copyright.)... 

FIGURE 11.9 Displacement separation of a crude MSH mixture with the same column used as in Figure 11.8. Carrier 0.25% formic acid, 0.5% triethylamine, 19% acetonitrile displacer, 50mM BDMA in 0.25% formic acid, 0.5% triethylamine, 21% acetonitrile. Flow rate O.lmL/min feed 35 mg MSH. (Reprinted with permission from Shukla, A.A. et ah, Biotechnol. Prog., 14, 92, 1998. Copyright 1998, American Chemical Society.)... 

Of particular interest in the case of the displacement separation of the melanotropins, acetonitrile was mixed with both the carrier and the displacer. The purpose was to suppress the sigmoidal isotherm of MSH which was then found to underlie the Langmuirian isotherm of the displacer in the area of operational interest. The idea of isotherm suppression through use of acetonitrile/displacer mixtures surfaced again later in the Horvath laboratory (see below). 

The band of the second component in the displacement separation has an apparent efficiency of 160,000 theoretical plates while the simulated column only has 3,600 theoretical plates. The squeeze effect on component 2 in the displacement separation is important resulting in a band that is 7 times... 

FIGURE 11.12 Hypothetical displacement separation of a three-component mixture containing two trace components loaded at 0.1 mg each and a major component loaded at 20mg. Panel a, main component band and displacer front panel b, peaks of the impurities panel c, peak of the second component under analytical (linear elution) conditions. (Reprinted with permission from Elsevier from Viscomi, G.C. et ah, J. Chromatogr., 440, 157, 1988. Copyright.)... 

FIGURE 11.14 Concept of EMDC. Panel A, in conventional displacement, separation times are long (on the order of honrs) and components form highly concentrated zones near the displacer front, some mixed with the displacer. Panel B, in elntion modified displacement, acetonitrile is added to the carrier and to the displacer solution in a targeted way to effect elntion of some components and displacement of others. Other components are mixed with the displacer. Rnn times are <1 h. (Reprinted with permission from Elsevier from Kalghatgi, K. et al., J. Chromatogr., 604,47, 1992. Copyright.)... 

Another apparatus for general biaxial extension testing, illustrated in Fig. 8, was built at our laboratory27). A square sheet of rubber, 11.5 cm long and 1 mm thick, is clamped at the edges by several pieces of movable chucks and stretched biaxially by means of the two bars that can be displaced separately bade and forth by a servo-meachnism. Tensile forces acting on the sheet in the stretching directions are transmitted to the bars and measured by two transducers mounted at the ends of each bar. After many modifications and improvements on the mechanical and electric parts,... 

FIGURE 4 (A) Adsorption isotherms of bovine and horse heart cytochrome c each at two different salt concentrations (90 and 125 m/W). Column 50 X 5 mm i.d. strong cation exchanger (8 (im) flow rate 0.2 mL/min. (Kundu et al.49) (B) Displacement separation of cytochrome c s from bovine and horse heart using BAEE as the displacer. Column 105 X 5 mm i.d. strong cation exchanger (8 /im) mobile phase 50 m/VI sodium phosphate buffer, pH 6.0 feed 1.6 mL of 0.52 m M each of bovine and horse heart cytochrome c in carrier displacer concentration 40 mAI N-a-benzoyl arginine ethyl ester (BAEE) in the carrier flow rate 0.2 mL / min fraction size 200 mL. 

FIGURE 8 Displacement histogram and UV detector trace for a selective displacement process. (A) Displacement separation of a three-component protein mixture using streptomycin sulfate A as a displacer. Column 100 X 5 mm i.d. strong cation exchange (8 m) carrier 30 mM sodium phosphate buffer, pH 6.0 feed 1.6 mL of 0.392 mAI ribonudease A, 0.42 mM horse cytochrome c and 0.34 mM lysozyme in the carrier. Total column loading 12.7 mg/mL column displacer 25 mM streptomycin sulfate A flow rate 0.2 mL/min fraction size 200 /iL. (Kundu et al.43) (B) UV detector trace monitored at 280 nm for the displacement separation shown below. 

The steric mass action (SMA) model has been shown to successfully predict nonlinear, multicomponent behavior in ion-exchange systems over a range of mobile phase salt concentrations.71-75 It has also been widely employed as a methods development tool for displacement separations.42,45,50 In this section, we will describe several graphical techniques derived this theory which can facilitate methods development in ion-exchange displacement systems. 

It has been shown by a stability analysis71 that the measure of relative affinities in a displacement separation is the dynamic affinity of a species which is given by... 

A schematic for developing displacement separations is shown in Fig. 12. The first step consists of selecting a stationary phase and mobile phase conditions which result in the greatest selectivity for the separation problem at hand. The SMA parameters of the principal components of the mixture should then be determined as described earlier. 

The development of displacement separations has historically been an empirical process and even though chromatographic theory may guide the selection of operating conditions the final stage must involve experimental validation. Typically, several experiments will be carried out at or near the conditions determined by the theory. The final stage in the procedure is either experimental or numerical optimization of the displacement process to produce optimal yields, purities and productivities. At this point, the relative efficacy of selective and conventional displacement chromatography can also be evaluated. 

Conductive parts of an intrinsically safe circuit shall be separated from those of non-intrinsically safe circuits or from other i-circuits in order to strictly prevent any voltage transfer or current displacement. Separation elements are clearances (in air), distances through a casting compound or a... 

Figure 6 Distribution of component concentrations as a function of column height during separation of a three-component mixture (a) frontal separation (b) displacement separation.

Solution can be collected from the zone containing B and A while the BX can be obtained from it upon frontal separation (Fig. 9). The ion-exchange resin leaving column II returns to the zone of column I from which solution is collected. Concentrated A and C impurities are removed from time to time at the ends of column I near flow reversal zones. It is also possible to use an auxiliary section in column II to displace separated ions from ion exchanger by the better sorbed E ions. 

Displacement TLC (D-TLC) has been applied to scout for the optimum of conditions for high-performance displacement chromatography. Advantages in the use of a planar displacement separation involve the easy and continuous observation of the displacing procedure itself through the separation. That process involves ... 

Ci2-Cig olefins are prepared by a modified Ziegler a-olefin process based on ethylene and triethylaluminum. The process consists of five steps buildup, displacement, separation, alkylation, and recycle. The major chemical and economic problems encountered are wide molecular weight distribution of the products and incomplete recovery of triethylaluminum. Catalysts consisting of alkyl-aluminums and colloidal nickel are needed for the alkylation-displacement steps however, the omount of nickel has to be very low because in the other process steps, nickel favors side reactions. The yield of a-olefins in the C 2" i8 creased by using coordination compounds of triethylaluminum with a Lewis base followed by azeotropic distillation. In the Chlorex process, (bis-a-chloroethyl) ether is used because of easy availability and low cost. 

The major steps in the process are buildup, displacement, separation, and alkylation. A convenient starting point in analyzing the system is the eflfluent from the displacement reactor. The stream at this point consists primarily of triethylaluminum, ethylene, a-olefins from Ce to Cjg and above, and minor quantities of the nickel displacement catalyst. 

Following elution of the isotachic train and the displacer solution from the column, the column must be regenerated and reequilibrated with the carrier before any subsequent displacement separation. This reequilibration step can be lengthy and is frequently considered a major Umitation to efficient displacement operation. Displacement chromatography requires the competitive isotherms of the solutes and the displacer to be convex upward and to not intersect each other. (See the entry Distribution Coefficient for related information.)... 

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