Crystallization elution fractionation

Crystallization elution fractionation (CEF) is a new separation technique developed by Moiuabal [102] for the analysis of the CCD that combines the separation power of CRYSTAF and TREF. The CEF technique is based on a new and patented separation principle, referred to as dynamic crystallization (DC) [87], that separates fractions inside a column according to crystallizabUity while a small flow of solvent passes through the column. The separation by DC occurs during the crystallization step. CEF combines the separation power of DC in the crystallization step with the separation during dissolution of the TREF technique. 

Fig. 26 Separation by crystallizability (a) TREF separation process, (b) dynamic crystallization and crystallization elution fractionation. Tl initial crystallization and elution temperatures, TF final crystallization and elution temperatures, FE elution flow, FC crystallization flow...

CED Cohesive energy density CEF Crystallization elution fractionation CFC Cross-fractionation chromatography CFT Continuum field theory CGC Constrained geometry catalyst CHX Cyclohexyl... 

B. Monrabal, J. Sancho-Tello, N. Maya, L. Romero, Crystallization elution fractionation. A new separation process for polyolefin resins, in Encyclopedia of analytical chemistry, ed. by... 

K. Surlya, S. Anantawaraskul, J.B.P. Soares, Cocrystallization of ethylene/l-octene copolymer blends during crystallization analysis fractionation and crystallization elution fractionation. J. Polym. Sci. B Polym. Phys. 49, 678-684 (2011)... 

Anantawaraskul, S., Soares,. B. P. and Wood-Adams, P. M. Fractionation of Semicrystalline Polymers by Crystallization Analysis Fractionation and Temperature Rising Elution Fractionation. Vol. 182, pp. 1-54. 

Samples of branched polyethylene were investigated by the combination of crystal-lizability fractionation and fractionation by molar mass. The first step was the precipitation of the polymer sample onto the glass-beads in a column (150 x 8 mm) used for the fractionation by crystallinity. The precipitation was performed by cooling a solution of 10 g/1 polyethylene in o-dichlorobenzene from 140 to 40 °C within 60 min. Subsequently, the polymer was extracted from the column by the same solvent at stepwise increased temperature. In an example given, the first fraction was eluted at 40 °C and additional 17 fractions at temperatures each raised by 2-10 K. The finer steps were employed in the middle of the fractionation procedure the last one reached even from 110 to 140 °C. About 10 min equilibration time proved to be adequate. The fractions were analyzed subsequently by SEC on a polystyrene-gel column. The whole process was automated 128). 

The orange solid product was washed with water, dried in vacuum over P205, and chromatographed on an alkaline alumina column. The first fraction, 420 mg., yellow to pale orange crystals eluted with pentane-benzene, proved to be the principal constituent of the mixture. It was recrystallized from pentane-benzene to give a nearly colorless compound, m.p., 162.5°-163° C. Its infrared spectrum was identical with that of triphenylcarbinol, lit. m.p., 162.5° C. (11). 

Despite repeated recrystallizations, both diastereomers 43a and 43b were obtained only as amorphous solids. Therefore, the first-eluted fraction (-)-43a was reduced with LiAlH4 to yield enantiopure glycol (-)-42, which was further converted to 4-bromobenzoate (-)-44 (Fig. 9.7a). By recrystallization from EtOH, (-)-44 gave good single crystals suitable for X-ray analysis, and consequently its absolute configuration was explicitly determined as S by the Bijvoet pair measurement of the anomalous dispersion effect of the bromine atom contained (Fig. 9.7b) [40]. 

Polymers by Crystallization Analysis Fractionation and Temperature Rising Elution... 

Dr. Gene Ford identified a third fungus, EMIBD, as a Penicillium sp., most likely P. brevicompactum. When grown in mycological broth (21 days, unshaken) and harvested as described above, the methylene chloride extract of the filtrate was active against Candida albicans. When this extract was chromatographed on Sephadex LH-20 size exclusion gel (chloroform/methanol, 1 1) thirteen fractions eluted. All of the antifungal activity resided in fractions 6 and 7. Crystals in fraction 6 were removed by filtration. The crystalline compound was spectroscopically identical to mycophenolic acid (23) which was first identified over 50 years ago as the... 

Monrabal B (2000) Temperature rising elution Iractionation and crystallization analysis fractionation. In Meyers RA (ed) Encyclopedia of analytical chemistry. Wiley, Chichester, pp 8074-8094... 

Important data on physical architecture of crystallable polymers can be obtained from temperature rising elution fractionation, TREF and crystallization fractionation, CRYSTAF. 

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