Recent developments in gel permeation chromatography: high speed and high resolution

Analysis of Nonionic Surfactants with Polyoxyethylene Chains by High-Performance Liquid Chromatography

“…Separation is carried out in aqueous and non-aqueous solutions on silica, polystyrene and vinyl alcohol copolymer gels [50,98,99,138]. Separation of ethoxylates in SEC, when exclusion is the only separation mechanism, is usually much worse than in normal or reversed chromatography and does not provide complete oligomer resolution.…”

A twin‐column recycling chromatography with solvent gradient for reinforcing the isolation of minor impurities

“…In the second, a longer column might be adopted to provide satisfactory separations, but it would obviously lead to a higher column pressure and stricter requirement on equipment. Hence, some indirect methods were developed to extend the effective length of the column …”

“…Nevertheless, a part of the separation attained in the column will lose due to the significant band broadening caused by the pump. In order to overcome such deficiency, a twin‐column recycling chromatography is proposed as shown in Figure , in where two basically identical columns are connected through a 6‐port valve, and the solute bands are circulated in a closed loop of the two columns by switching the valve without flowing through the pump. As a result, the separation will be continuously improved as the number of cycle increases.…”

Theoretical study of recycling in preparative chromatography

“…Several successful applications of closed-loop recycling and alternate pumping have been reported in the field of gel permeation chromatography (Bombaugh et al, 1969Bombaugh, 1970;Duvdevani et al, 1971;Nakamura et al, 1973;Lesec et al, 1974;Lesec and Quivoron, 1976) for separations of enantiomers (Henry, 1974;Schlogl and Widhalm, 1984;Werner, 1989) and for the isolation of vitamins (Letter, 1992).…”