Gradient elution chromatography

Hardware contributions to gradient performance High-pressure or low-pressure gradient formation Mixing devices Gradient precision Developing a gradient separation The three basic situations 

Early components bunched, late components bunched Early components bunched, late components resolved Early components resolved, late components resolved Applying a strategy for developing a gradient separation Effect of flow rate upon gradient performance Applications Practical considerations 

Viscosity and refractive index effects In-line degassing Flow programming Summary References Acknowledgment 

FIGURE 7-1. Isocratic separations of polystyrene 800. Sample 50 fiL of 5% solution in THF. Column Radial-Pak Resolve C8 (10 /xm), 10 cm ID x 8 mm ID. Flow rate 1.0 mL/min. Detector model 40-254 nm. (a) 70% THF in water, (b) 60% THF in water, (c) mobile phase 50-70% THF in water using gradient curve shown on chromatogram for 20 min. Flow rate 2.5 mL/min. (Reproduced from reference 1 with permission.) 

FIGURE 7-2. Separation of UV-absorbing compounds found in hemodialysate fluid, (a) Standard compounds. (b) Solvent reservoir and mixing chamber. (Reproduced from reference 2 with permission.) 

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TABLE 16-14 Expressions for Predictions of Chromatographic Peak Properties in Linear Gradient Elution Chromatography under Trace Conditions with a Small Feed Injection and Inlet Gradient Described by op = opo + pt (Adapted from Refs. A and B). 

Schellinger, A. P., Carr, P. W. Isocratic and gradient elution chromatography a comparison in terms of speed, retention reprodudbility and quantitation. /. Chromatogr. A 2006, 1109, 253-255. 

Schwartz, H. E., Karger, B. L., and Kucera, F, Gradient elution chromatography with microbore columns, Anal. Chem., 55, 1752, 1983. 

In NP systems where the retention is controlled by the three-parameter retention equation (Equation 5.11), the elution volumes in normal-phase gradient-elution chromatography can be calculated using [55-57]... 

Thesenon-Emeric, G. and F.E. Regnier "Process Monitoring by Parallel Column Gradient Elution Chromatography. . -Statistical (in-on Sit".. 11 ]4 (June I. 1991). Wahl. J.H.. C.G. Eskc. and V.L. McGufTin "Solvent Modulation in Liquid t hru maiography." Analytical Chemistry. 1117 (June I. 1991). 

However CCR reduction in SCT SRC occurs with significant alteration of GEC classes, primarily toward the formation of less polar compounds. The classes of W. Kentucky SCT SRC, separated by GEC (gradient elution chromatography), are given in Table 2 and show that 75% of the SRC is polar and noneluted polar asphaltenes. 

C. Liteanu and S. Gocan, Gradient Elution Chromatography, Wiley, New York, 1974. 

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