Solvent gradient elution

Fig.6. Schematic of the solvent gradient elution CEC apparatus with ramping voltage accessory. (Reprinted with permission from [204] Copyright 1996 American Chemical Society)...

Human erythrocytes, peripheral leukocytes and liver have been satisfactorily analyzed, but it should be recognized that each different tissue source may require different extraction conditions and modified solvent gradient elution in order to obtain maximal recoveries and optimal chromatographic resolution of the tissue characteristic glycosphingolipids. Fletcher,... 

There remains some doubt concerning the optimum number of solvents to be employed in the multiple solvent, gradient elution programme. Scott and Kucera [243] recommend a 12 solvent series, while Snyder [244] proposed a six solvent series to cover the entire polarity range adequately. 

Fig. 2.7. Schematic diagram of the solvent gradient-elution CEC apparatus. (Reproduced from Ref. [29] with permission of the publisher).

Plasma ultrafiltrates were diltued 1 50 and analyzed by RP-HPLC (column packed with PLRP-S, Polymer Laboratories) with solvent gradient elution (acetonitrile-water from 15 85 to 90 10, 30 min), coupled to ICP-MS through a novel interface, allowing efficient elimination of acetonitrile... 

High-performetnce micro packed fused-silica and open-tubular glass capillary columns were prepared and applied to separations of complex mixtures. Solvent-gradient elution was quite useful for the separation of solutes with wide polarity. Instruments and some applications are described. 

Table 1. HPLC solvent gradient elution program...

Other methods for solvent fractionation are by precipitation method where a ratio of solvent and nonsolvent is incrementally adjusted from solvent-rich to nonsolvent-rich. In this technique, the higher molecular weight fractions will be precipitated first. A reverse technique is solvent gradient elution where a liquid mixture of increasing solvent power is used to remove the lowest molecular weight materials first (10). 

Fractionation of polyethylene has been accomplished by a wide variety of techniques other than size elution chromatography and temperature rising elution fractionation, with a multitude of variations thereon. The most notable of these less widely employed techniques include crystallization analysis fractionation [13], solvent gradient elution [14], successive solution fractionation (SSF) [15], continuous countercurrent extraction [16], high temperature thermal field-fiow fractionation [17], supercritical fluid fractionation (SCF) [18,19], and high pressure Soxhlet extraction [20]. 

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