title: Carbonaceous sorbents for high-temperature interactive liquid chromatography of polyolefins.
abstract: The elution behavior of polyethylene (PE) and the three stereoisomers of polypropylene (PP) was studied on porous graphite along with three other carbon-based sorbents, carbon-clad zirconia particles, activated carbon, and exfoliated graphite in a systematic way in this work. Decahydronaphthalene, 1,2,3,4-tetrahydronaphthalene, 1,3,5-trimethylbenzene, tetrachloroethylene, xylene and p-xylene were used as mobile phases. While PE is adsorbed to various extents on all the tested carbonaceous sorbents from the majority of the solvents, PP is fully adsorbed only in selected cases. Testing alcohols (C7-C9) as mobile phase with Hypercarb™ indicates that all stereoisomers of PP are selectively adsorbed and desorbed when a solvent gradient alcohol→1,2,4-trichlorobenzene is used at 160°C. The retention of all stereoisomers of PP increases with the polarity of the alcohol. Linear PE is retained on Hypercarb™ even from 1,2-dichloro- and 1,2,4-trichlorobenzene, when a temperature below 120°C is applied, while it is not retained from these solvents at higher temperatures. All stereoisomeric forms of PP are not adsorbed under the same conditions. Some of the tested new sorbent/solvent systems have potential to be applied in routine analysis of industrially synthesised polyolefins.
authors.affiliation: Fraunhofer Institute for Structural Durability and System Reliability, Division Plastics, Group Material Analytics, Darmstadt, Germany.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Chitta
authors.forename: Tibor
authors.initials: T
authors.lastname: Macko
authors.forename: Robert
authors.initials: R
authors.lastname: Brüll
authors.forename: Matthew
authors.initials: M
authors.lastname: Miller
authors.forename: Rongjuan
authors.initials: R
authors.lastname: Cong
authors.forename: Willem
authors.initials: W
authors.lastname: deGroot
keywords: Carbon sorbents; Ethylene-propylene copolymers; LC; Polyethylene; Polypropylene